src/lib: Remove unnecessary code

Fix the following warnings detected by checkpatch.pl:

WARNING: break is not useful after a goto or return
WARNING: Statements terminations use 1 semicolon
WARNING: else is not generally useful after a break or return
WARNING: void function return statements are not generally useful

TEST=Build and run on Galileo Gen2

Change-Id: I6f095c4e9cb1ee4ff2ebdf095ef612e1a8393231
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18762
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/lib/prog_loaders.c

@@ -166,7 +166,6 @@ static struct prog global_payload =
 
 void __attribute__((weak)) mirror_payload(struct prog *payload)
 {
-	return;
 }
 
 void payload_load(void)