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

Some of these can be changed from #if to if(), but that will happen
in a follow-on commmit.

Change-Id: Ib3a1cf04482a8f19b159c31cfb16a7b492748d91
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20352
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/drivers/elog/boot_count.c

@@ -27,7 +27,7 @@
  * This can either be declared as part of the option
  * table or statically defined in the board config.
  */
-#if CONFIG_USE_OPTION_TABLE
+#if IS_ENABLED(CONFIG_USE_OPTION_TABLE)
 # include "option_table.h"
 # define BOOT_COUNT_CMOS_OFFSET (CMOS_VSTART_boot_count_offset >> 3)
 #else