security/vboot/bootmode: Add weak fill_lb_gpios

This change allows VBOOT to build when the mainboard hasn't implemented
any of the VBOOT functions yet.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I42ca8f0dba9fd4a868bc7b636e4ed04cbf8dfab0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50341
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/security/vboot/bootmode.c

@@ -72,4 +72,8 @@ int __weak get_recovery_mode_switch(void)
 	return 0;
 }
 
+void __weak fill_lb_gpios(struct lb_gpios *gpios)
+{
+}
+
 #endif