[new uImage] rework error handling so common functions don't reset

Changed image_get_ramdisk() to just return NULL on error and have
get_ramdisk() propogate that error to the caller.  It's left to the
caller to call do_reset() if it wants to.

Also moved calling do_reset() in get_fdt() and fdt_relocate() on ppc
to a common location.  In the future we will change get_fdt() and
fdt_relocate() to return success/failure and not call do_reset() at all.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Marian Balakowicz <m8@semihalf.com>
diff --git a/include/image.h b/include/image.h
index 1cec1db..025ec0f 100644
--- a/include/image.h
+++ b/include/image.h
@@ -382,7 +382,7 @@
 int gen_image_get_format (void *img_addr);
 ulong gen_get_image (ulong img_addr);
 
-void get_ramdisk (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],
+int get_ramdisk (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],
 		bootm_headers_t *images, uint8_t arch,
 		ulong *rd_start, ulong *rd_end);