net: dsa: sja1105: unconditionally free old gating config

Currently sja1105_compose_gating_subschedule is not prepared to be
called for the case where we want to recompute the global tc-gate
configuration after we've deleted those actions on a port.

After deleting the tc-gate actions on the last port, max_cycle_time
would become zero, and that would incorrectly prevent
sja1105_free_gating_config from getting called.

So move the freeing function above the check for the need to apply a new
configuration.

Fixes: 834f8933 ("net: dsa: sja1105: implement tc-gate using time-triggered virtual links")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>