staging: mt7621-pci: use pcie_[read|write] in RALINK_PCI_PCICFG_ADDR and RALINK_PCI_PCIMSK_ADDR

RALINK_PCI_PCICFG_ADDR and RALINK_PCI_PCIMSK_ADDR are defined to be directly
referenced for read and write. Use pcie_read and pcie_write instead changing
its definition to a simple relative offset to pcie base address.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Tested-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>