mainboard/[g-l]: add IS_ENABLED() around Kconfig symbol references

Change-Id: I1f906c8c465108017bc4d08534653233078ef32d
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20343
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/mainboard/google/foster/chromeos.c

@@ -68,7 +68,7 @@ void fill_lb_gpios(struct lb_gpios *gpios)
 
 int get_recovery_mode_switch(void)
 {
-#if CONFIG_EC_GOOGLE_CHROMEEC
+#if IS_ENABLED(CONFIG_EC_GOOGLE_CHROMEEC)
 	uint32_t ec_events;
 
 	ec_events = google_chromeec_get_events_b();