RDMA/core: Avoid unnecessary sa_family overwrite

addr4_resolve() and addr6_resolve() are called by checking the value of
sa_family.

Both above functions overwrite the value after typecasting, this is not
necessary.

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>