imx: Add support for i.MX28 based XEA board

This patch introduces support for i.MX28 based XEA board.

This board supports DM/DTS in U-Boot proper as well as DM aware drivers
in SPL (u-boot.sb) by using OF_PLATDATA.
More detailed information regarding usage of it can be found in
./board/liebherr/xea/README file.

U-Boot SPL 2019.10-rc1-00233-g6aa549f05c (Aug 12 2019 - 09:23:36 +0200)
Trying to boot from MMC1
MMC0: Command 8 timeout (status 0xf0344020)
mmc_load_image_raw_sector: mmc block read error

U-Boot 2019.10-rc1-00233-g6aa549f05c (Aug 12 2019 - 09:23:36 +0200)

CPU:   Freescale i.MX28 rev1.2 at 454 MHz
BOOT:  SSP SPI #3, master, 3V3 NOR
Model: Liebherr (LWE) XEA i.MX28 Board
DRAM:  128 MiB
MMC:   MXS MMC: 0
Loading Environment from SPI Flash... SF: Detected n25q128a13 with page size 256 Bytes, erase size 64 KiB, total 16 MiB
OK
In:    serial
Out:   serial
Err:   serial
Net:
Warning: ethernet@800f0000 (eth0) using random MAC address - ce:e1:9e:46:f3:a2
eth0: ethernet@800f0000
Hit any key to stop autoboot:  0

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/arch/arm/dts/imx28-xea-u-boot.dtsi b/arch/arm/dts/imx28-xea-u-boot.dtsi
new file mode 100644
index 0000000..cc2ced5
--- /dev/null
+++ b/arch/arm/dts/imx28-xea-u-boot.dtsi
@@ -0,0 +1,46 @@
+// 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 eMMC driver
+ * configuration in SPL for falcon boot.
+ */
+#include "imx28-u-boot.dtsi"
+/ {
+	apb@80000000 {
+		u-boot,dm-spl;
+
+		apbh@80000000 {
+			u-boot,dm-spl;
+		};
+
+		apbx@80040000 {
+			u-boot,dm-spl;
+		};
+	};
+};
+
+&clks {
+	u-boot,dm-spl;
+};
+
+&gpio0 {
+	u-boot,dm-spl;
+};
+
+&pinctrl {
+	u-boot,dm-spl;
+};
+
+&ssp0 {
+	u-boot,dm-spl;
+};
+
+&ssp3 {
+	u-boot,dm-spl;
+};