net: dsa: mt7530: set STP state on filter ID 1

As filter ID 1 is the only one used for bridges, set STP state on it.

Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>