RDMA/mlx5: Fix counter update on MR cache mkey creation

RDMA/mlx5: Fix counter update on MR cache mkey creation

After an mkey is created, update the counter for pending mkeys before
reshceduling the work that is filling the cache.

Rescheduling the work with a full MR cache entry and a wrong 'pending'
counter will cause us to miss disabling the fill_to_high_water flag.
Thus leaving the cache full but with an indication that it's still
needs to be filled up to it's full size (2 * limit).
Next time an mkey will be taken from the cache, we'll unnecessarily
continue the process of filling the cache to it's full size.

Fixes: 57e7071683ef ("RDMA/mlx5: Implement mkeys management via LIFO queue")
Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Link: https://patch.msgid.link/0f44f462ba22e45f72cb3d0ec6a748634086b8d0.1725362530.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>