RDMA/mlx5: Delete one-time used functions

Merge them into their callers, usually the only thing the caller did was
to call the one function, so this is clearer.

Link: https://lore.kernel.org/r/20200702081809.423482-7-leon@kernel.org


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