mfd: rtsx_usb: Avoid setting ucr->current_sg.status

mfd: rtsx_usb: Avoid setting ucr->current_sg.status

commit 8dcc5ff8fcaf778bb57ab4448fedca9e381d088f upstream.

Member "status" of struct usb_sg_request is managed by usb core. A
spin lock is used to serialize the change of it. The driver could
check the value of req->status, but should avoid changing it without
the hold of the spinlock. Otherwise, it could cause race or error
in usb core.

This patch could be backported to stable kernels with version later
than v3.14.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Roger Tseng <rogerable@realtek.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>