xhci: fix write to USB3_PSSEN and XUSB2PRM pci config registers

The function pci_write_config_dword() sets the appropriate byteordering
internally so the value argument should not be converted to little-endian.
This bug was found by sparse.

This patch is not suitable for stable.  Since cpu_to_lei32 is a no-op on
little endian systems, this bug would only affect big endian Intel
systems with the EHCI to xHCI port switchover, which are non-existent,
AFAIK.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>