ext4_utils: refactor kernel headers

Move the kernel header includes into a single include file that
can deal with getting the kernel int types correct on all
platforms.

Change-Id: Ied3dc6a0f5cbb3ceb686aa3de72f16e10a36462a
diff --git a/ext4_utils/xattr.h b/ext4_utils/xattr.h
index 60c01ce..0f323fd 100644
--- a/ext4_utils/xattr.h
+++ b/ext4_utils/xattr.h
@@ -40,6 +40,6 @@
      (char *)(entry) + EXT4_XATTR_LEN((entry)->e_name_len)))
 #define EXT4_XATTR_SIZE(size) \
     (((size) + EXT4_XATTR_ROUND) & ~EXT4_XATTR_ROUND)
-#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
+#define IS_LAST_ENTRY(entry) (*(uint32_t *)(entry) == 0)
 
 #endif /* !_SYSTEM_EXTRAS_EXT4_UTILS_XATTR_H */