ARM: dts: keystone-k2g-evm: fix rgmii phy-mode for ksz9031 phy

ARM: dts: keystone-k2g-evm: fix rgmii phy-mode for ksz9031 phy

Since commit 4570040da42c ("net: phy: micrel: add phy-mode support for the
KSZ9031 PHY") the networking is broken on keystone-k2g-evm board.

The above board have phy-mode = "rgmii-id" and it is worked before because
KSZ9031 PHY started with default RGMII internal delays configuration (TX
off, RX on 1.2 ns) and MAC provided TX delay by default.
After above commit, the KSZ9031 PHY starts handling phy mode properly and
enables both RX and TX delays, as result networking is become broken.

Fix it by switching to phy-mode = "rgmii-rxid" to reflect previous
behavior.

Fixes: 4570040da42c ("net: phy: micrel: add phy-mode support for the KSZ9031 PHY")
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>