ARM: dts: Add dtsi files for AM3703, AM3715 and DM3725

DM3730 is considered as omap36xx.dtsi, while the rest has:
     DM3730 | DM3725 | AM3715 | AM3703
IVA    X    |   X    |        |
SGX    X    |        |   X    |
Where X is "supported"
Signed-off-by: André Hentschel <nerv@dawncrow.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am3703.dtsi

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 André Hentschel <nerv@dawncrow.de>
+ */
+
+#include "omap36xx.dtsi"
+
+&iva {
+	status = "disabled";
+};
+
+&sgx_module {
+	status = "disabled";
+};

arch/arm/boot/dts/am3715.dtsi

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 André Hentschel <nerv@dawncrow.de>
+ */
+
+#include "omap36xx.dtsi"
+
+&iva {
+	status = "disabled";
+};

arch/arm/boot/dts/dm3725.dtsi

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 André Hentschel <nerv@dawncrow.de>
+ */
+
+#include "omap36xx.dtsi"
+
+&sgx_module {
+	status = "disabled";
+};