DTS: Add imx6q-display5-u-boot.dtsi file with u-boot specific properties

This file setups UART5 based serial to be used as pre-relocation
console in the U-Boot proper.

On purpose pinux configuration is omitted here as it has been already
done in SPL. For early pre-relocation code we only need the serial
device from DTS.
Signed-off-by: NLukasz Majewski <lukma@denx.de>
Reviewed-by: NPeng Fan <peng.fan@nxp.com>

arch/arm/dts/imx6q-display5-u-boot.dtsi

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019
+ * Lukasz Majewski, DENX Software Engineering, lukma@denx.de
+ *
+ * SPDX-License-Identifier:     GPL-2.0+ or X11
+ */
+
+/*
+ * The minimal augmentation DTS U-Boot file to allow UART5
+ * configuration in the pre-relocation stage of U-Boot
+ * proper.
+ *
+ * As the same UART is already configured in SPL, we don't need
+ * setup pinmux for it again.
+ */
+
+/ {
+	aliases {
+		mmc0 = &usdhc4;
+	};
+
+	soc {
+		u-boot,dm-pre-reloc;
+
+		aips-bus@2100000 {
+			u-boot,dm-pre-reloc;
+		};
+	};
+
+	chosen {
+		stdout-path = &uart5;
+	};
+};
+
+&i2c3 {
+	at24@50 {
+		u-boot,i2c-offset-len = <2>;
+	};
+};
+
+&uart5 {
+	u-boot,dm-pre-reloc;
+};