arch/x86: Clean up CONFIG_SMP and MAX_CPUS test

Change-Id: I7c138758707f87c0d7a827b6887c7752d3714cde
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/21088
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/smp/node.h

@@ -7,4 +7,9 @@ int boot_cpu(void);
 #define boot_cpu(x) 1
 #endif
 
+static inline int is_smp_boot(void)
+{
+	return IS_ENABLED(CONFIG_SMP) && CONFIG_MAX_CPUS > 1;
+}
+
 #endif /* _SMP_NODE_H_ */