net: dsa: mt7530: fix VLAN traffic leaks

PCR_MATRIX field was set to all 1's when VLAN filtering is enabled, but
was not reset when it is disabled, which may cause traffic leaks:

	ip link add br0 type bridge vlan_filtering 1
	ip link add br1 type bridge vlan_filtering 1
	ip link set swp0 master br0
	ip link set swp1 master br1
	ip link set br0 type bridge vlan_filtering 0
	ip link set br1 type bridge vlan_filtering 0
	# traffic in br0 and br1 will start leaking to each other

As port_bridge_{add,del} have set up PCR_MATRIX properly, remove the
PCR_MATRIX write from mt7530_port_set_vlan_aware.

Fixes: 83163f7d

 ("net: dsa: mediatek: add VLAN support for MT7530")
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>