usb: wusbcore: implement hwahc_op_get_frame_number

This patch adds an implementation for hwahc_op_get_frame_number.  The
request is fulfulled by forwarding it to the lower hcd.  This was done
because the GET_TIME request on the HWA requires sending an URB to the
HWA and waiting for the results which cannot be done in atomic context.

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