IB/mlx5: Introduce and use mkey context setting helper routine

Introduce and use set_mkc_access_pd_addr_fields() which sets mkey
context's access rights, PD, address fields.  Thereby avoid the code
duplication.

Link: https://lore.kernel.org/r/20191006155443.31068-1-leon@kernel.org


Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>