tools/mkimage: fix compiler warnings, use "const"

This fixes some compiler warnings:
tools/default_image.c:141: warning: initialization from incompatible pointer type
tools/fit_image.c:202: warning: initialization from incompatible pointer type
and changes to code to use "const" attributes in a few places where
it's appropriate.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/include/image.h b/include/image.h
index beb3a16..a62669f 100644
--- a/include/image.h
+++ b/include/image.h
@@ -333,7 +333,7 @@
 }
 
 #define image_get_hdr_l(f) \
-	static inline uint32_t image_get_##f(image_header_t *hdr) \
+	static inline uint32_t image_get_##f(const image_header_t *hdr) \
 	{ \
 		return uimage_to_cpu (hdr->ih_##f); \
 	}
@@ -346,7 +346,7 @@
 image_get_hdr_l (dcrc);		/* image_get_dcrc */
 
 #define image_get_hdr_b(f) \
-	static inline uint8_t image_get_##f(image_header_t *hdr) \
+	static inline uint8_t image_get_##f(const image_header_t *hdr) \
 	{ \
 		return hdr->ih_##f; \
 	}
@@ -355,12 +355,12 @@
 image_get_hdr_b (type);		/* image_get_type */
 image_get_hdr_b (comp);		/* image_get_comp */
 
-static inline char *image_get_name (image_header_t *hdr)
+static inline char *image_get_name (const image_header_t *hdr)
 {
 	return (char *)hdr->ih_name;
 }
 
-static inline uint32_t image_get_data_size (image_header_t *hdr)
+static inline uint32_t image_get_data_size (const image_header_t *hdr)
 {
 	return image_get_size (hdr);
 }
@@ -376,16 +376,16 @@
  * returns:
  *     image payload data start address
  */
-static inline ulong image_get_data (image_header_t *hdr)
+static inline ulong image_get_data (const image_header_t *hdr)
 {
 	return ((ulong)hdr + image_get_header_size ());
 }
 
-static inline uint32_t image_get_image_size (image_header_t *hdr)
+static inline uint32_t image_get_image_size (const image_header_t *hdr)
 {
 	return (image_get_size (hdr) + image_get_header_size ());
 }
-static inline ulong image_get_image_end (image_header_t *hdr)
+static inline ulong image_get_image_end (const image_header_t *hdr)
 {
 	return ((ulong)hdr + image_get_image_size (hdr));
 }
@@ -418,8 +418,8 @@
 	strncpy (image_get_name (hdr), name, IH_NMLEN);
 }
 
-int image_check_hcrc (image_header_t *hdr);
-int image_check_dcrc (image_header_t *hdr);
+int image_check_hcrc (const image_header_t *hdr);
+int image_check_dcrc (const image_header_t *hdr);
 #ifndef USE_HOSTCC
 int getenv_yesno (char *var);
 ulong getenv_bootm_low(void);
@@ -427,31 +427,31 @@
 void memmove_wd (void *to, void *from, size_t len, ulong chunksz);
 #endif
 
-static inline int image_check_magic (image_header_t *hdr)
+static inline int image_check_magic (const image_header_t *hdr)
 {
 	return (image_get_magic (hdr) == IH_MAGIC);
 }
-static inline int image_check_type (image_header_t *hdr, uint8_t type)
+static inline int image_check_type (const image_header_t *hdr, uint8_t type)
 {
 	return (image_get_type (hdr) == type);
 }
-static inline int image_check_arch (image_header_t *hdr, uint8_t arch)
+static inline int image_check_arch (const image_header_t *hdr, uint8_t arch)
 {
 	return (image_get_arch (hdr) == arch);
 }
-static inline int image_check_os (image_header_t *hdr, uint8_t os)
+static inline int image_check_os (const image_header_t *hdr, uint8_t os)
 {
 	return (image_get_os (hdr) == os);
 }
 
-ulong image_multi_count (image_header_t *hdr);
-void image_multi_getimg (image_header_t *hdr, ulong idx,
+ulong image_multi_count (const image_header_t *hdr);
+void image_multi_getimg (const image_header_t *hdr, ulong idx,
 			ulong *data, ulong *len);
 
-void image_print_contents (image_header_t *hdr);
+void image_print_contents (const void *hdr);
 
 #ifndef USE_HOSTCC
-static inline int image_check_target_arch (image_header_t *hdr)
+static inline int image_check_target_arch (const image_header_t *hdr)
 {
 #if defined(__ARM__)
 	if (!image_check_arch (hdr, IH_ARCH_ARM))