USB: Support for submitting control URBs under xHCI.

Warn users of URB_NO_SETUP_DMA_MAP about xHCI behavior.

Device drivers can choose to DMA map the setup packet of a control transfer
before submitting the URB to the USB core.  Drivers then set the
URB_NO_SETUP_DMA_MAP and pass in the DMA memory address in setup_dma, instead of
providing a kernel address for setup_packet.  However, xHCI requires that the
setup packet be copied into an internal data structure, and we need a kernel
memory address pointer for that.  Warn users of URB_NO_SETUP_DMA_MAP that they
should provide a valid pointer for setup_packet, along with the DMA address.

FIXME:  I'm not entirely sure how to work around this in the xHCI driver
or USB core.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>