image: Correct the OS location code to work on sandbox

A recent change broke the 'bootm' command on sandbox. The root cause is
using a pointer as an address. Conversion from pointer to address needs to
use map_to_sysmem() so that sandbox can do the right thing. The problem was
pre-existing but uncovered by a recent commit.

Fix this. Also move fit_get_end() to the C file to avoid needing to include
mapmem.h (and thus asm/io.h) everywhere.

Fixes: 1fec3c5d (common/image.c: Make boot_get_ramdisk() perform a check for Android images)

Signed-off-by: Simon Glass <sjg@chromium.org>

include/image.h

@@ -818,10 +818,7 @@ static inline ulong fit_get_size(const void *fit)
  * returns:
  *     end address of the FIT image (blob) in memory
  */
-static inline ulong fit_get_end(const void *fit)
-{
-	return (ulong)fit + fdt_totalsize(fit);
-}
+ulong fit_get_end(const void *fit);
 
 /**
  * fit_get_name - get FIT node name