usb: host: xhci-plat: add support for the R-Car H2 and M2 xHCI controllers

The R-Car H2 and M2 SoCs come with an xHCI controller that requires
some specific initializations related to the firmware downloading and
some specific registers. This patch adds the support for this special
configuration as an xHCI quirk executed during probe and start.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: "mathias.nyman@intel.com" <mathias.nyman@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>