IB/mlx5: Create UMR QP just before first reg_mr occurs

UMR QP is not used in some cases, so move QP and its CQ creations from
driver load flow to the time first reg_mr occurs, that is when MR
interfaces are first called.

The initialization of dev->umrc.pd and dev->umrc.lock is still done in
driver load because pd is needed for mlx5_mkey_cache_init and the lock
is reused to protect against the concurrent creation.

When testing 4G bytes memory registration latency with rtool [1] and 8
threads in parallel, there is minor performance degradation (<5% for
the max latency) is seen for the first reg_mr with this change.

Link: https://github.com/paravmellanox/rtool

 [1]

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Link: https://lore.kernel.org/r/55d3c4f8a542fd974d8a4c5816eccfb318a59b38.1717409369.git.leon@kernel.org


Signed-off-by: Leon Romanovsky <leon@kernel.org>