PCI: rcar-gen2: Rename rcar_pci_priv to rcar_pci

Rename struct rcar_pci_priv to rcar_pci to match the convention of
<driver>_pci. No functional change intended.

Link: https://lore.kernel.org/r/20211223011054.1227810-19-helgaas@kernel.org


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>