RDMA/core: Let protocol specific function typecast sockaddr structure

Current code typecasts destination address using extra variable but uses
source address as is.

Even though the compiler optimizes such code well, just let each protocol
specific function typecast for src and dest both and have symmetric code.

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