x86, pci: Exclude Moorestown PCI code if CONFIG_X86_MRST=n

If we don't have any Moorestown CPU support compiled in, we don't need
the Moorestown PCI support either.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4B858E89.7040807@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/pci/Makefile

@@ -13,7 +13,9 @@ obj-$(CONFIG_X86_VISWS)		+= visws.o
 
 obj-$(CONFIG_X86_NUMAQ)		+= numaq_32.o
 
-obj-y				+= common.o early.o mrst.o
+obj-$(CONFIG_X86_MRST)		+= mrst.o
+
+obj-y				+= common.o early.o
 obj-y				+= amd_bus.o
 obj-$(CONFIG_X86_64)		+= bus_numa.o