cpu/intel: 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: Ie685bbbb1cbf06d32631ea40ad120b6f45374b2e
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20336
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/cpu/intel/model_2065x/bootblock.c

@@ -23,7 +23,7 @@
 
 #include <cpu/intel/microcode/microcode.c>
 
-#if CONFIG_SOUTHBRIDGE_INTEL_IBEXPEAK
+#if IS_ENABLED(CONFIG_SOUTHBRIDGE_INTEL_IBEXPEAK)
 #include <southbridge/intel/ibexpeak/pch.h>
 #include "model_2065x.h"
 #else

src/cpu/intel/model_2065x/model_2065x_init.c

@@ -295,7 +295,7 @@ static void intel_cores_init(struct device *cpu)
 		       cpu->path.apic.apic_id,
 		       new->path.apic.apic_id);
 
-#if CONFIG_SMP && CONFIG_MAX_CPUS > 1
+#if IS_ENABLED(CONFIG_SMP) && CONFIG_MAX_CPUS > 1
 		/* Start the new CPU */
 		if (!start_cpu(new)) {
 			/* Record the error in cpu? */