usb: host: xhci-plat: Add reset support

Add optional reset support. This is in preparation to adding USB xHCI
support for RZ/V2M SoC.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230121145853.4792-9-biju.das.jz@bp.renesas.com


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