mtrr: fix UP breakage caused during switch to stop_machine

While removing custom rendezvous code and switching to stop_machine,
commit 192d8857427d ("x86, mtrr: use stop_machine APIs for doing MTRR
rendezvous") completely dropped mtrr setting code on !CONFIG_SMP
breaking MTRR settting on UP.

Fix it by removing the incorrect CONFIG_SMP.

Signed-off-by: Tejun Heo <[e-mail]>
Reported-by: Anders Eriksson <[e-mail]>
Tested-and-acked-by: Suresh Siddha <[e-mail]>
Acked-by: H. Peter Anvin <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86/kernel/cpu/mtrr/main.c

···
  */
 static int mtrr_rendezvous_handler(void *info)
 {
-#ifdef CONFIG_SMP
 	struct set_mtrr_data *data = info;
 
 	/*
···
 	} else if (mtrr_aps_delayed_init || !cpu_online(smp_processor_id())) {
 		mtrr_if->set_all();
 	}
-#endif
 	return 0;
 }