board: gateworks: venice: add imx8mp-venice-gw740x support

The GW74xx is based on the i.MX 8M Plus SoC featuring:
 - LPDDR4 DRAM
 - eMMC FLASH
 - Gateworks System Controller
 - PCIe Gen 3.0 switch (build option)
 - USB 3.0 HUB
 - USB Type-C front panel connector
 - GPS
 - 3-axis accelerometer
 - CAN bus
 - 6x GbE RJ45 front-panel jacks
  - 1x IMX8M FEC RGMII GbE (with Passive PoE)
  - 5x IMX8M EQOS RGMII 6 port GbE Switch
    (1x with 802.3af class 5 Active PoE)
 - RS232/RS485/RS422 serial transceiver
 - MIPI header (DSI/CSI/GPIO/PWM/I2S)
 - DigI/O header (UART/GPIO/I2C/ADC)
 - 802.11ac WiFi
 - Bluetooth BLE
 - 3x MiniPCIe sockets with PCI/USB
 - 1x M.2 Socket with USB2.0, PCIe, and dual-SIM
 - PMIC
 - Wide range DC input supply (8V to 60V DC)

Do the following to add support for this and future imx8mp-venice boards:
 - add dts
 - add DRAM config
 - add PMIC config
 - add IMX8MP support in spl.c and venice.c

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/arch/arm/dts/imx8mp-venice-u-boot.dtsi b/arch/arm/dts/imx8mp-venice-u-boot.dtsi
new file mode 100644
index 0000000..37f3edc
--- /dev/null
+++ b/arch/arm/dts/imx8mp-venice-u-boot.dtsi
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright 2022 Gateworks Corporation
+ */
+
+#include "imx8mp-u-boot.dtsi"
+
+/ {
+	wdt-reboot {
+		compatible = "wdt-reboot";
+		wdt = <&wdog1>;
+		u-boot,dm-spl;
+	};
+};
+
+&gpio1 {
+	u-boot,dm-spl;
+};
+
+&gpio2 {
+	u-boot,dm-spl;
+};
+
+&gpio3 {
+	u-boot,dm-spl;
+};
+
+&gpio4 {
+	u-boot,dm-spl;
+};
+
+&gpio5 {
+	u-boot,dm-spl;
+};
+
+&uart2 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_uart2 {
+	u-boot,dm-spl;
+};
+
+&usdhc3 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_usdhc3 {
+	u-boot,dm-spl;
+};
+
+&i2c1 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_i2c1 {
+	u-boot,dm-spl;
+};
+
+&gsc {
+	u-boot,dm-spl;
+};
+
+&i2c2 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_i2c2 {
+	u-boot,dm-spl;
+};
+
+&wdog1 {
+	u-boot,dm-spl;
+};