USB: whci-hcd: support urbs with scatter-gather lists

Support urbs with scatter-gather lists by trying to fit sg list elements
into page lists in one or more qTDs.  qTDs must end on a wMaxPacketSize
boundary so if this isn't possible the urb's sg list must be copied into
bounce buffers.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>