Revert "PCI: rcar: Build pcie-rcar.c only on ARM"

Now that we can build on arm64, revert commit 7c537c67
("PCI: rcar: Build pcie-rcar.c only on ARM").

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>