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/uart/util.c

@@ -13,14 +13,14 @@
 
 #include <console/console.h>
 #include <console/uart.h>
-#if CONFIG_USE_OPTION_TABLE
+#if IS_ENABLED(CONFIG_USE_OPTION_TABLE)
 #include <option.h>
 #include "option_table.h"
 #endif
 
 unsigned int default_baudrate(void)
 {
-#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE
+#if !defined(__SMM__) && IS_ENABLED(CONFIG_USE_OPTION_TABLE)
 	static const unsigned baud[8] =
 		{ 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200 };
 	unsigned b_index = 0;