mainboard/[a-e]: add IS_ENABLED() around Kconfig symbol references

Change-Id: Icca8bac5e67f83dfc5a8f5ef1cb87c6432e0a236
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20342
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/mainboard/aopen/dxplplusu/romstage.c b/src/mainboard/aopen/dxplplusu/romstage.c
index 3fba1ad..f79d3d3 100644
--- a/src/mainboard/aopen/dxplplusu/romstage.c
+++ b/src/mainboard/aopen/dxplplusu/romstage.c
@@ -65,8 +65,8 @@
 		 * is lost. Only return addresses from main() and
 		 * scrub_ecc() are recovered to stack via xmm0-xmm3.
 		 */
-#if CONFIG_HW_SCRUBBER
-#if !CONFIG_USBDEBUG_IN_ROMSTAGE
+#if IS_ENABLED(CONFIG_HW_SCRUBBER)
+#if !IS_ENABLED(CONFIG_USBDEBUG_IN_ROMSTAGE)
 		unsigned long ret_addr = (unsigned long)((unsigned long*)&bist - 1);
 		e7505_mch_scrub_ecc(ret_addr);
 #endif