The function searches used_mask for a set bit in a for-loop bit by bit.
Simplify it by using atomic find_and_set_bit(), and make a nice
one-liner.
Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Acked-by: Vinod Koul <vkoul@xxxxxxxxxx>