usb: host: xhci: plat: make use of new methods in xhci_plat_priv

Now that the code has been refactored enough,
switching over to using ->plat_start() and
->init_quirk() becomes a very simple patch.

After this patch, there are no further uses for
xhci_plat_type_is() which will be removed in a
follow-up patch.

Acked-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>