net: phy: mediatek: add MT7530 & MT7531's PHY ID macros

This patch adds MT7530 & MT7531's PHY ID macros in mtk-ge.c so that
it follows the same rule of mtk-ge-soc.c.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: SkyLake.Huang <skylake.huang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>