ublk: consolidate UBLK_IO_FLAG_OWNED_BY_SRV checks

ublk: consolidate UBLK_IO_FLAG_OWNED_BY_SRV checks

Every ublk I/O command except UBLK_IO_FETCH_REQ checks that the ublk_io
has UBLK_IO_FLAG_OWNED_BY_SRV set. Consolidate the separate checks into
a single one in __ublk_ch_uring_cmd(), analogous to those for
UBLK_IO_FLAG_ACTIVE and UBLK_IO_FLAG_NEED_GET_DATA.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250505172624.1121839-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>