x86: ivybridge: Add northbridge init functions

Add init for the northbridge, another part of the platform controller hub.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/ivybridge/Makefile b/arch/x86/cpu/ivybridge/Makefile
index 95491b5..1296a78 100644
--- a/arch/x86/cpu/ivybridge/Makefile
+++ b/arch/x86/cpu/ivybridge/Makefile
@@ -13,6 +13,7 @@
 obj-y += me_status.o
 obj-y += model_206ax.o
 obj-y += microcode_intel.o
+obj-y += northbridge.o
 obj-y += pch.o
 obj-y += pci.o
 obj-y += report_platform.o