ARM: dts: imx6q-prti6q: fix PHY address

Due to bug in the bootloader, the PHY has floating address and may
randomly change on each PHY reset. To avoid it, the updated bootloader
with the following patch[0] should be used:

| ARM: protonic: disable on-die termination to fix PHY bootstrapping
|
| If on-die termination is enabled, the RXC pin of iMX6 will be pulled
| high. Since we already have an 10K pull-down on board, the RXC level on
| PHY reset will be ~800mV, which is mostly interpreted as 1. On some
| reboots we get 0 instead and kernel can't detect the PHY properly.
|
| Since the default 0x020e07ac value is 0, it is sufficient to remove this
| entry from the affected imxcfg files.
|
| Since we get stable 0 on pin PHYADDR[2], the PHY address is changed from
| 4 to 0.

With latest bootloader update, the PHY address will be fixed to "0".

[0] https://git.pengutronix.de/cgit/barebox/commit/?id=93f7dcf631edfcda19e7757b28d66017ea274b81

Fixes: 0d446a5055 ("ARM: dts: add Protonic PRTI6Q board")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6q-prti6q.dts

@@ -213,8 +213,8 @@
 		#size-cells = <0>;
 
 		/* Microchip KSZ9031RNX PHY */
-		rgmii_phy: ethernet-phy@4 {
-			reg = <4>;
+		rgmii_phy: ethernet-phy@0 {
+			reg = <0>;
 			interrupts-extended = <&gpio1 28 IRQ_TYPE_LEVEL_LOW>;
 			reset-gpios = <&gpio1 25 GPIO_ACTIVE_LOW>;
 			reset-assert-us = <10000>;