ublk_drv: fix double shift bug

The test/clear_bit() functions take a bit number, but this code is
passing as shifted value.  It's the equivalent of saying BIT(BIT(0))
instead of just BIT(0).

This doesn't affect runtime because numbers are small and it's done
consistently.

Fixes: fa362045 ("ublk: simplify ublk_ch_open and ublk_ch_release")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/Yt/2R/+MJf/MSoyl@kili


Signed-off-by: Jens Axboe <axboe@kernel.dk>