Reduce deep nesting of header files

Reduce the number of header files included from other header
files as much as possible without splitting the files. Use forward
declarations where possible. This allows removal of some unnecessary
"#ifndef __ASSEMBLY__" statements.

Also, review the .c and .S files for which header files really need
including and reorder the #include statements alphabetically.

Fixes ARM-software/tf-issues#31

Change-Id: Iec92fb976334c77453e010b60bcf56f3be72bd3e
diff --git a/include/lib/io_storage.h b/include/lib/io_storage.h
index 59fd3f4..b6c5f9f 100644
--- a/include/lib/io_storage.h
+++ b/include/lib/io_storage.h
@@ -31,10 +31,7 @@
 #ifndef __IO_H__
 #define __IO_H__
 
-#ifndef __ASSEMBLY__
-
-#include <stdint.h>
-#include <stdio.h>	/* For ssize_t */
+#include <stdio.h> /* For ssize_t */
 
 
 /* Device type which can be used to enable policy decisions about which device
@@ -128,5 +125,4 @@
 int io_close(io_handle handle);
 
 
-#endif /* __ASSEMBLY__ */
 #endif /* __IO_H__ */