pci: Only link pci_rom.o in some cases

The content of pci_rom.c is only used in a few cases.  Only build and
link in these cases to avoid a global variable as gcc doesn't always
discard those when they are unused.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 219473a..da8b826 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -4,12 +4,12 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
 ifneq ($(CONFIG_DM_PCI),)
-obj-y += pci_rom.o
+obj-$(CONFIG_DM_VIDEO) += pci_rom.o
 obj-$(CONFIG_PCI) += pci-uclass.o pci_auto.o
 obj-$(CONFIG_DM_PCI_COMPAT) += pci_compat.o
 obj-$(CONFIG_PCI_SANDBOX) += pci_sandbox.o
 obj-$(CONFIG_SANDBOX) += pci-emul-uclass.o
-obj-$(CONFIG_X86) += pci_x86.o
+obj-$(CONFIG_X86) += pci_x86.o pci_rom.o
 else
 obj-$(CONFIG_PCI) += pci.o pci_auto_old.o
 endif