usb: xhci: Add support for URB_ZERO_PACKET to bulk/sg transfers

This commit checks for the URB_ZERO_PACKET flag and creates an extra
zero-length td if the urb transfer length is a multiple of the endpoint's
max packet length.

Signed-off-by: Reyad Attiyat <reyad.attiyat@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>