BACKPORT: block: Initialize bio priority earlier

Bio's IO priority needs to be initialized before we try to merge the bio
with other bios. Otherwise we could merge bios which would otherwise
receive different IO priorities leading to possible QoS issues.

Bug: 315228086
Bug: 307161346
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Change-Id: I6a28ae88242c4ebe69569ebe898f2cbe1042c5e6
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220623074840.5960-8-jack@suse.cz


Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit 9c6227e0)
[xiuhong: Resolved minor conflict in block/blk-mq.c]
Signed-off-by: Xiuhong Wang <xiuhong.wang@unisoc.com>