arm-trusted-firmware-mediatek: enable built-in 2.5G PHY on MT7988

Always enable built-in 2.5G PHY on MT7988 for now, so that it can be
used. In future it would be nice to be able to switch power and MDIO
access via address 0 at run-time in Linux, both, to be able to use
external PHYs at address 0 and to reduce power consumption on systems
not using the built-in 2.5G PHY.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/boot/arm-trusted-firmware-mediatek/patches/001-mt7988-enable-2p5g-phy.patch

@@ -0,0 +1,11 @@
+--- a/plat/mediatek/mt7988/bl2/bl2_plat_init.c
++++ b/plat/mediatek/mt7988/bl2/bl2_plat_init.c
+@@ -90,6 +90,8 @@ static void mtk_i2p5g_phy_init(void)
+ 	 * clear bit 22 to use external MDIO.
+ 	 */
+ 	mmio_setbits_32(GBE_TOP_REG, I2P5G_MDIO);
++	/* Internal 2.5Gphy power on sequence */
++	eth_2p5g_phy_mtcmos_ctrl(true);
+ }
+ 
+ static void mt7988_i2c_init(void)