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/smp/atomic.h

@@ -1,7 +1,7 @@
 #ifndef SMP_ATOMIC_H
 #define SMP_ATOMIC_H
 
-#if CONFIG_SMP
+#if IS_ENABLED(CONFIG_SMP)
 #include <arch/smp/atomic.h>
 #else
 

src/include/smp/node.h

@@ -1,7 +1,7 @@
 #ifndef _SMP_NODE_H_
 #define _SMP_NODE_H_
 
-#if CONFIG_SMP
+#if IS_ENABLED(CONFIG_SMP)
 int boot_cpu(void);
 #else
 #define boot_cpu(x) 1

src/include/smp/spinlock.h

@@ -1,7 +1,7 @@
 #ifndef SMP_SPINLOCK_H
 #define SMP_SPINLOCK_H
 
-#if CONFIG_SMP
+#if IS_ENABLED(CONFIG_SMP)
 #include <arch/smp/spinlock.h>
 #else /* !CONFIG_SMP */