x86: only compile setup_percpu.o on SMP

Impact: Minor build optimization
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

arch/x86/kernel/Makefile

@@ -28,7 +28,7 @@ CFLAGS_paravirt.o	:= $(nostackp)
 obj-y			:= process_$(BITS).o signal.o entry_$(BITS).o
 obj-y			+= traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
 obj-y			+= time_$(BITS).o ioport.o ldt.o dumpstack.o
-obj-y			+= setup.o i8259.o irqinit_$(BITS).o setup_percpu.o
+obj-y			+= setup.o i8259.o irqinit_$(BITS).o
 obj-$(CONFIG_X86_VISWS)	+= visws_quirks.o
 obj-$(CONFIG_X86_32)	+= probe_roms_32.o
 obj-$(CONFIG_X86_32)	+= sys_i386_32.o i386_ksyms_32.o
@@ -59,6 +59,7 @@ apm-y				:= apm_32.o
 obj-$(CONFIG_APM)		+= apm.o
 obj-$(CONFIG_X86_SMP)		+= smp.o
 obj-$(CONFIG_X86_SMP)		+= smpboot.o tsc_sync.o ipi.o
+obj-$(CONFIG_SMP)		+= setup_percpu.o
 obj-$(CONFIG_X86_32_SMP)	+= smpcommon.o
 obj-$(CONFIG_X86_64_SMP)	+= tsc_sync.o smpcommon.o
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline_$(BITS).o

arch/x86/kernel/setup_percpu.c

@@ -22,14 +22,8 @@
 # define DBG(x...)
 #endif
 
-/*
- * Could be inside CONFIG_HAVE_SETUP_PER_CPU_AREA with other stuff but
- * voyager wants cpu_number too.
- */
-#ifdef CONFIG_SMP
 DEFINE_PER_CPU(int, cpu_number);
 EXPORT_PER_CPU_SYMBOL(cpu_number);
-#endif
 
 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA