MIPS: ath79: add PCI_AR724X Kconfig symbol

The AR724X specific PCI code can be used for the
AR934X SoCs, however it can be selected only if
SOC_AR724X is set.

Introduce a new Kconfig symbol in order to be able
to use the code for AR934X as well.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Cc: linux-mips@linux-mips.org
Cc: mcgrof@infradead.org
Patchwork: https://patchwork.linux-mips.org/patch/3514/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/Makefile

@@ -20,7 +20,7 @@ obj-$(CONFIG_BCM63XX)		+= pci-bcm63xx.o fixup-bcm63xx.o \
 					ops-bcm63xx.o
 obj-$(CONFIG_MIPS_ALCHEMY)	+= pci-alchemy.o
 obj-$(CONFIG_SOC_AR71XX)	+= pci-ar71xx.o
-obj-$(CONFIG_SOC_AR724X)	+= pci-ar724x.o
+obj-$(CONFIG_PCI_AR724X)	+= pci-ar724x.o
 
 #
 # These are still pretty much in the old state, watch, go blind.