net: dsa: Avoid cross-chip syncing of VLAN filtering

In the Linux kernel, the following vulnerability has been resolved:

net: dsa: Avoid cross-chip syncing of VLAN filtering

Changes to VLAN filtering are not applicable to cross-chip
notifications.

On a system like this:

.-----. .-----. .-----.
| sw1 +---+ sw2 +---+ sw3 |
'-1-2-' '-1-2-' '-1-2-'

Before this change, upon sw1p1 leaving a bridge, a call to
dsa_port_vlan_filtering would also be made to sw2p1 and sw3p1.

In this scenario:

.---------. .-----. .-----.
| sw1 +---+ sw2 +---+ sw3 |
'-1-2-3-4-' '-1-2-' '-1-2-'

When sw1p4 would leave a bridge, dsa_port_vlan_filtering would be
called for sw2 and sw3 with a non-existing port - leading to array
out-of-bounds accesses and crashes on mv88e6xxx.