S2io: two branches the same in wait_for_cmd_complete()

Fix check to verify if a register bit is set. We have not hit this bug because
wait_for_cmd_complete() is always called with S2IO_BIT_RESET.
Reported by Roel Kluin <roel.kluin@gmail.com>.

Signed-off-by: Ram Vepa <ram.vepa@neterion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>