QP type is stored in the IB/core QP struct, but it doesn't have all the
needed information, like internal QP type used in the driver itself.
Update mlx5_ib to have cached QP type which includes both IBTA and
Mellanox specific one.

Such change allows us to make even further cleanup of QP creation flow.

Link: https://lore.kernel.org/r/20200427154636.381474-21-leon@kernel.orgReviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>