usb: gadget: udc-xilinx: fix restricted __le16 degrades to integer warning

usb_ctrlrequest members wValue and wIndex are of type __le16, so to fix
this warnings we are using le16_to_cpu() macros.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202209020044.CX2PfZzM-lkp@intel.com/
Signed-off-by: Piyush Mehta <piyush.mehta@amd.com>
Link: https://lore.kernel.org/r/20230822063201.16929-2-piyush.mehta@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>