mlxsw: core: Do not use EMADs in mlxsw_emad_fini

Be symmetric with mlxsw_emad_init and don't use EMADs in mlxsw_emad_fini
cleanup function. Use command interface instead.

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