x86: Don't enable SMP in SPL

SMP should be set up in U-Boot where possible, not SPL. Disable it in SPL.
For 64-bit U-Boot we should find a way to allow SMP operations in U-Boot,
but this is somewhat more complicated. For now that is disabled too.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
diff --git a/arch/x86/cpu/Makefile b/arch/x86/cpu/Makefile
index ee0499f..16e67e3 100644
--- a/arch/x86/cpu/Makefile
+++ b/arch/x86/cpu/Makefile
@@ -60,7 +60,7 @@
 obj-$(CONFIG_$(SPL_TPL_)X86_32BIT_INIT) += irq.o
 endif
 ifndef CONFIG_$(SPL_)X86_64
-obj-$(CONFIG_SMP) += mp_init.o
+obj-$(CONFIG_$(SPL_)SMP) += mp_init.o
 endif
 obj-y += mtrr.o
 obj-$(CONFIG_PCI) += pci.o