usb: wusbcore: move isoc_frame_index from wa_xfer to wa_seg

If multiple segments belonging to an isoc transfer are submitted
concurrently, the isoc_frame_index field in struct wa_xfer can get
corrupted.  This patch moves the isoc_frame_index field from struct
wa_xfer to struct wa_seg to prevent this from happening.

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