include/uapi/linux/blkzoned.h: Remove a superfluous __packed directive

Using the __packed directive for a structure that does not need
it is wrong because it makes gcc generate suboptimal code on some
architectures. Hence remove the __packed directive from the
blk_zone_report structure definition. See also
http://digitalvampire.org/blog/index.php/2006/07/31/why-you-shouldnt-use-__attribute__packed/

.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Matias Bjorling <mb@lightnvm.io>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>