stm32mp: add syscon for STGEN

Add STGEN as SYSCON device: allow access to device address
defined in device tree

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/mach-stm32mp/syscon.c b/arch/arm/mach-stm32mp/syscon.c
new file mode 100644
index 0000000..5641745
--- /dev/null
+++ b/arch/arm/mach-stm32mp/syscon.c
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2018, STMicroelectronics - All Rights Reserved
+ *
+ * SPDX-License-Identifier:	GPL-2.0+	BSD-3-Clause
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <syscon.h>
+#include <asm/arch/stm32.h>
+
+static const struct udevice_id stm32mp_syscon_ids[] = {
+	{ .compatible = "st,stm32-stgen",
+	  .data = STM32MP_SYSCON_STGEN },
+	{ }
+};
+
+U_BOOT_DRIVER(syscon_stm32mp) = {
+	.name = "stmp32mp_syscon",
+	.id = UCLASS_SYSCON,
+	.of_match = stm32mp_syscon_ids,
+	.bind = dm_scan_fdt_dev,
+};