usb: appledisplay: Set urb transfer_flags to URB_NO_TRANSFER_DMA_MAP

The driver does allocate a DMA address with usb_alloc_coherent but did
not set the appropriate flag to signal that transfer_dma is set to a
valid value.

Signed-off-by: Alexander Theissen <alex.theissen@me.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>