xhci: workaround for AMD Promontory disabled ports wakeup

For AMD Promontory xHCI host, although you can disable USB ports in
BIOS settings, those ports will be enabled anyway after you remove a
device on that port and re-plug it in again. It's a known limitation of
the chip. As a workaround we can clear the PORT_WAKE_BITS.

[commit and code comment rephrasing -Mathias]
Signed-off-by: Joe Lee <asmt.swfae@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>