oslib: blkzoned: add blkzoned_move_zone_wp() helper function

oslib: blkzoned: add blkzoned_move_zone_wp() helper function

As a preparation for continue_on_error option support for zonemode=zbd,
introduce a new function blkzoned_move_zone_wp(). It moves the write
pointer by data write. If data buffer is provided, call pwrite() system
call. If data buffer is not provided, call fallocate() to write zero
data.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20250425052148.126788-2-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>