null_blk: add trace in null_blk_zoned.c

With the help of previously added tracepoints we can now trace
report-zones, zone-write and zone-mgmt ops in null_blk_zoned.c.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>