x86/PCI: use -DDEBUG when CONFIG_PCI_DEBUG set

We use dev_dbg() in arch/x86/pci, but there's no easy way to turn it
on.  Add -DDEBUG when CONFIG_PCI_DEBUG=y, just like we do in drivers/pci.
Signed-off-by: NBjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

arch/x86/pci/Makefile

@@ -16,3 +16,7 @@ obj-$(CONFIG_X86_NUMAQ)		+= numaq_32.o
 obj-y				+= common.o early.o
 obj-y				+= amd_bus.o
 obj-$(CONFIG_X86_64)		+= intel_bus.o
+
+ifeq ($(CONFIG_PCI_DEBUG),y)
+EXTRA_CFLAGS += -DDEBUG
+endif