scsi: sd_zbc: Do not write lock zones for reset

Resetting a zone write pointer is equivalent to discarding sectors:
after a reset, the zone sectors will contain zeros (or the format
pattern). So there is no need for mutual exclusion between a zone reset
and write. Similarly to discard, make it the responsability of the user
to properly synchronize between reset and write (as is done now for
discard and write).

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>