security/vboot: Remove duplicate offsetof() definition

This macro is already defined in commonlib/helpers.h

Change-Id: I1fce2936757b13807e254f4a844f583b938bf349
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37181
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Alex James <theracermaster@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/security/vboot/secdata_tpm.c

@@ -40,10 +40,6 @@
 #include <vb2_api.h>
 #include <console/console.h>
 
-#ifndef offsetof
-#define offsetof(A,B) __builtin_offsetof(A,B)
-#endif
-
 #ifdef FOR_TEST
 #include <stdio.h>
 #define VBDEBUG(format, args...) printf(format, ## args)