net: dsa: b53: Remove is_cpu_port()

This is not used anywhere, so remove it.
Reviewed-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_priv.h

@@ -186,11 +186,6 @@ static inline int is58xx(struct b53_device *dev)
 #define B53_CPU_PORT_25	5
 #define B53_CPU_PORT	8
 
-static inline int is_cpu_port(struct b53_device *dev, int port)
-{
-	return dev->cpu_port;
-}
-
 struct b53_device *b53_switch_alloc(struct device *base,
 				    const struct b53_io_ops *ops,
 				    void *priv);