null_blk: Simplify null_zone_write()

null_blk: Simplify null_zone_write()

In null_zone_write, we do not need to first check if the target zone
condition is FULL, READONLY or OFFLINE: for theses conditions, the check
of the command sector against the zone write pointer will always result
in the command failing. Remove these checks.

We still however need to check that the target zone write pointer is not
invalid for zone append operations. To do so, add the macro
NULL_ZONE_INVALID_WP and use it in null_set_zone_cond() when changing a
zone to READONLY or OFFLINE condition.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20240411085502.728558-4-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>