x86: build fix

Impact: build fix on certain UP configs

fix:

 arch/x86/kernel/cpu/common.c: In function 'cpu_init':
 arch/x86/kernel/cpu/common.c:1141: error: 'boot_cpu_id' undeclared (first use in this function)
 arch/x86/kernel/cpu/common.c:1141: error: (Each undeclared identifier is reported only once
 arch/x86/kernel/cpu/common.c:1141: error: for each function it appears in.)

Pull in asm/smp.h on UP, so that we get the definition of
boot_cpu_id.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/common.c

@@ -20,6 +20,7 @@
 #include <asm/pat.h>
 #include <asm/asm.h>
 #include <asm/numa.h>
+#include <asm/smp.h>
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/mpspec.h>
 #include <asm/apic.h>