PCI: rcar: Rename pcie-rcar.c to pcie-rcar-host.c

PCI: rcar: Rename pcie-rcar.c to pcie-rcar-host.c

This commit renames pcie-rcar.c to pcie-rcar-host.c in preparation for
adding support for endpoint mode. CONFIG_PCIE_RCAR is kept so that arm64
defconfig change can be a separate patch.

With this patch both config options PCIE_RCAR and PCIE_RCAR_HOST will be
available but PCIE_RCAR internally selects PCIE_RCAR_HOST so that bisect
builds wont be affected.

Link: https://lore.kernel.org/r/1588854799-13710-2-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>