Some rockchip platforms (e.g. rk3399, rk3328) xHCI controller
support stream for UASP (USB Attached SCSI PROTOCOL), use of
UAS generally provides faster transfers compared to the older
USB Mass Storage Bulk-Only Transport (BOT) drivers.
Change-Id: I67ce5cdb821413d3c4d018be31c892d20d831470 Signed-off-by: William Wu <wulf@rock-chips.com>