ublk: add helpers to check ublk_device flags

ublk: add helpers to check ublk_device flags

Introduce ublk_device analogues of the ublk_queue flag helpers:
- ublk_support_zero_copy() -> ublk_dev_support_user_copy()
- ublk_support_auto_buf_reg() -> ublk_dev_support_auto_buf_reg()
- ublk_support_user_copy() -> ublk_dev_support_user_copy()
- ublk_need_map_io() -> ublk_dev_need_map_io()
- ublk_need_req_ref() -> ublk_dev_need_req_ref()
- ublk_need_get_data() -> ublk_dev_need_get_data()

These will be used in subsequent changes to avoid accessing the
ublk_queue just for the flags, and instead use the ublk_device.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>