net: dsa: lan9303: define LAN9303_NUM_PORTS 3

Will be used instead of '3' in upcomming patches.
Signed-off-by: Egil Hjelmeland <privat@egil-hjelmeland.no>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/lan9303-core.c

@@ -20,6 +20,8 @@
 
 #include "lan9303.h"
 
+#define LAN9303_NUM_PORTS 3
+
 /* 13.2 System Control and Status Registers
  * Multiply register number by 4 to get address offset.
  */