ARM: i.MX8MN: assume USBOTG power domains to be powered

When i.MX8MN support was first added, upstream device tree did list no
power domains. Now it does and we defer probe of USB indefinitely
because we have no power domain driver. If we need to do PCI on the
i.MX8MM in barebox, there'll likely be no way around importing the power
domain driver, but for USB which used to work, only thing we need to do
is ignore the new power domain specification. Do so by adding the
new barebox,allow-dummy property to the new known-enabled power domain.

Fixes: b01786b ("dts: update to v5.18-rc1")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20220808140035.1672733-4-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/dts/imx8mn-evk.dts

@@ -7,6 +7,7 @@
 /dts-v1/;
 
 #include <arm64/freescale/imx8mn-evk.dts>
+#include "imx8mn.dtsi"
 
 / {
 	chosen {

arch/arm/dts/imx8mn.dtsi

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+
+&pgc_otg1 {
+	barebox,allow-dummy;
+};