usb: host: xhci-rcar: remove leftover quirk handling

Loading V3 firmware does not need a quirk anymore, remove the leftover
code.

Fixes: ed8603e1 ("usb: host: xhci-rcar: Simplify getting the firmware name for R-Car Gen3")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20230307163041.3815-10-wsa+renesas@sang-engineering.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>