mtip32xx: avoid to read HOST_CAP from HW in .queue_rq()
It is observed reading the register from HW takes a bit long,
for example in my box, the following difference of 'perf report
--no-children fio ...' can be seen when running I/O:
2) V4.12 with the following patch
+ 9.14% fio [mtip32xx] [k] mtip_irq_handler
......
+ 1.14% fio [mtip32xx] [k] mtip_init_cmd_header
IOPS can be increased by ~5% with this patch too.
Fixes: a4e84aae8139(mtip32xx: use runtime tag to initialize command header) Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>