net: dsa: ksz: use common define for tag len

Remove special taglen define KSZ8795_INGRESS_TAG_LEN
and use generic KSZ_INGRESS_TAG_LEN instead.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>