vboot: Add new function for logging recovery mode switches

BUG=chrome-os-partner:59352
BRANCH=None
TEST=Compiles successfully

Change-Id: I87cd675ea45a8b05a178cf64119bf5f9d8d218ca
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/17408
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/vendorcode/google/chromeos/chromeos.c

@@ -33,3 +33,8 @@ int __attribute__((weak)) get_sw_write_protect_state(void)
 	// Can be implemented by a platform / mainboard
 	return 0;
 }
+
+void __attribute__((weak)) log_recovery_mode_switch(void)
+{
+	// Weak implementation. Nothing to do.
+}