net: dsa: mv88e6xxx: assign dynamic FDB to VLANs

Add a _mv88e6xxx_fid_new function which gives and flushes the lowest FID
available. Call it when preparing a new VTU entry.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/mv88e6xxx.h b/drivers/net/dsa/mv88e6xxx.h
index 6a30bda..9df331e 100644
--- a/drivers/net/dsa/mv88e6xxx.h
+++ b/drivers/net/dsa/mv88e6xxx.h
@@ -355,6 +355,8 @@
 #define GLOBAL2_QOS_WEIGHT	0x1c
 #define GLOBAL2_MISC		0x1d
 
+#define MV88E6XXX_N_FID		4096
+
 struct mv88e6xxx_switch_id {
 	u16 id;
 	char *name;