ARM: multi_v7_defconfig: Enable CONFIG_PCI_DRA7XX (Host & Device modes)

Enable CONFIG_PCI_DRA7XX in order to be able to configure PCIe
controller present in dra7 SoCs in both host mode and device mode.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>