ublk: remove redundant zone op check in ublk_setup_iod()

ublk_setup_iod() checks first whether the request is a zoned operation
issued to a device without zoned support and returns BLK_STS_IOERR if
so. However, such a request would already hit the default case in the
subsequent switch statement and fail the ublk_queue_is_zoned() check,
which also results in a return of BLK_STS_IOERR. So remove the redundant
early check for unsupported zone ops.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>