cbfs: remove unused code and prototype

The code is wrong (it's calling ntohl on an entry point that is actually
already le due to an old cbfs bug) and nothing calls it any more anyway.

Change-Id: Ief2c33faf99e3d2fc410524a5aae7bde378f088b
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: http://review.coreboot.org/4090
Tested-by: build bot (Jenkins)
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/include/cbfs.h

@@ -52,7 +52,6 @@
 
 #include <cbfs_core.h>
 
-int cbfs_execute_stage(struct cbfs_media *media, const char *name);
 void *cbfs_load_optionrom(struct cbfs_media *media, uint16_t vendor,
 			  uint16_t device, void * dest);
 void *cbfs_load_payload(struct cbfs_media *media, const char *name);