PCI: rcar: Remove DRV_NAME macro

The DRV_NAME macro is only used once, so there's no real advantage to
having the macro at all.  Remove it and use the "rcar-pcie" name directly
in the struct platform_driver.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>