util/amdfwtool: Include the header with __packed definition

Checkpatch script recommends to use __packed instead of
__attribute__((packed)). Currently the build rule for amdfwtool does not
include the required header file with __packed definition. Update the
compiler flag to include the required header file.

BUG=None
TEST=Build amdfwtool.

Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Change-Id: I448cbad533608dd5c2bd4f2d827fcc5db5dee5cb
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67384
Reviewed-by: Jon Murphy <jpmurphy@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/amdfwtool/amdfwtool.h

@@ -3,6 +3,7 @@
 #ifndef _AMD_FW_TOOL_H_
 #define _AMD_FW_TOOL_H_
 
+#include <commonlib/bsd/compiler.h>
 #include <stdint.h>
 #include <stdbool.h>