src: include <assert.h> when appropriate

Change-Id: Ib843eb7144b7dc2932931b9e8f3f1d816bcc1e1a
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/26796
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: David Guckian

src/security/vboot/vbnv_flash.c

@@ -14,7 +14,6 @@
  */
 
 #include <arch/early_variables.h>
-#include <assert.h>
 #include <commonlib/region.h>
 #include <console/console.h>
 #include <string.h>