commonlib/helpers: Add helper macro for member_size

member_size macro provides the size of a structure member.

Change-Id: I53e9c9bf70b3ebed0d15e8258111b17e50667a74
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/19384
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/commonlib/include/commonlib/helpers.h

@@ -85,6 +85,9 @@
 	const __typeof__(((type *)0)->member) *__mptr = (ptr);	\
 	(type *)((char *)__mptr - offsetof(type, member)); })
 
+/* Calculate size of structure member. */
+#define member_size(type, member)	(sizeof(((type *)0)->member))
+
 #ifndef __unused
 #define __unused __attribute__((unused))
 #endif