x86: initialize per-cpu GDT segment in per-cpu setup

Impact: cleanup

Rename init_gdt() to setup_percpu_segment(), and move it to
setup_percpu.c.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 73de055..37fa30b 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -60,8 +60,7 @@
 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_64_SMP)	+= tsc_sync.o
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline_$(BITS).o
 obj-$(CONFIG_X86_MPPARSE)	+= mpparse.o
 obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o nmi.o