usb: host: xhci-plat: add firmware_name in xhci_plat_priv

This patch adds a member "firmware_name" in struct xhci_plat_priv
to simplify the code to match specific firmware name.

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