RDMA/mlx5: Delete unsupported QP types

There is no need to explicitly check unsupported QP types,
rely on  "default" keyword in switch-case to catch them.

Link: https://lore.kernel.org/r/20200427154636.381474-20-leon@kernel.org


Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>