block: make REQ_OP_ZONE_OPEN a write operation

A REQ_OP_OPEN_ZONE request changes the condition of a sequential zone of
a zoned block device to the explicitly open condition
(BLK_ZONE_COND_EXP_OPEN). As such, it should be considered a write
operation.

Change this operation code to be an odd number to reflect this. The
following operation numbers are changed to keep the numbering compact.

No problems were reported without this change as this operation has no
data. However, this unifies the zone operation to reflect that they
modify the device state and also allows strengthening checks in the
block layer, e.g. checking if this operation is not issued against a
read-only device.

Fixes: 6c1b1da5 ("block: add zone open, close and finish operations")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>