x86: Add an SPL implementation

SPL needs to set up the machine ready for loading 64-bit U-Boot and jumping
to it. Call the existing init routines in order to accomplish this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 723288f..67117c3 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -37,6 +37,7 @@
 obj-y	+= tables.o
 obj-$(CONFIG_CMD_ZBOOT)	+= zimage.o
 obj-$(CONFIG_HAVE_FSP) += fsp/
+obj-$(CONFIG_SPL_BUILD) += spl.o
 
 extra-$(CONFIG_USE_PRIVATE_LIBGCC) += lib.a