mlxsw: core: Fix arg name of MLXSW_CORE_RES_VALID and MLXSW_CORE_RES_GET

First arg of these helpers should be "mlxsw_core".

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>