net: mvneta: add RGMII_RXID and RGMII_TXID support

RGMII_RXID and RGMII_TX_ID share the same GMAC CTRL setting as RGMII
or RGMII_ID.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>