net: dsa: Keep the vlan_filtering setting in dsa_switch if it's global

The current behavior is not as obvious as one would assume (which is
that, if the driver set vlan_filtering_is_global = 1, then checking any
dp->vlan_filtering would yield the same result). Only the ports which
are actively enslaved into a bridge would have vlan_filtering set.

This makes it tricky for drivers to check what the global state is.
So fix this and make the struct dsa_switch hold this global setting.

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

include/net/dsa.h

@@ -233,6 +233,11 @@ struct dsa_switch {
 	 */
 	bool			vlan_filtering_is_global;
 
+	/* In case vlan_filtering_is_global is set, the VLAN awareness state
+	 * should be retrieved from here and not from the per-port settings.
+	 */
+	bool			vlan_filtering;
+
 	unsigned long		*bitmap;
 	unsigned long		_bitmap;