src/include: add IS_ENABLED() around Kconfig symbol references

Change-Id: I2fbe6376a1cf98d328464556917638a5679641d2
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20354
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/include/option.h

@@ -6,7 +6,7 @@
  * storage can be used. This will benefit machines without CMOS as well as those
  * without a battery-backed CMOS (e.g. some laptops).
  */
-#if CONFIG_USE_OPTION_TABLE
+#if IS_ENABLED(CONFIG_USE_OPTION_TABLE)
 #include <pc80/mc146818rtc.h>
 #else
 #include <types.h>