cbfs: remove prepare() callback from struct cbfs_locator

The prepare() callback is no longer utilized in the code. Remove
the callback and support for it.

Change-Id: Ic438e5a80850a3df619dbbfdecb522a9dc2c1949
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36690
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Wim Vervoorn <wvervoorn@eltan.com>

src/lib/prog_loaders.c

@@ -43,8 +43,6 @@ int prog_locate(struct prog *prog)
 	if (prog_locate_hook(prog))
 		return -1;
 
-	cbfs_prepare_program_locate();
-
 	if (cbfs_boot_locate(&file, prog_name(prog), NULL))
 		return -1;