usb: wire adapter: add scatter gather support

This patch adds support for scatter gather DMA to the wire adapter and
updates the HWA to advertise support for SG transfers.  This allows the
block layer to submit transfer requests to the HWA HC without first
breaking them up into PAGE_SIZE requests.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>