arm: soc: move arm SoCs to top-dir

Move the SoC outside of the architecture tree and put them at the same
level as boards and architectures allowing both SoCs and boards to be
maintained outside the tree.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

soc/arm/st_stm32/stm32f7/Kconfig.soc

@@ -0,0 +1,21 @@
+# Kconfig.soc - ST Microelectronics STM32F7 MCU line
+#
+# Copyright (c) 2018 Yurii Hamann
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+choice
+prompt "STM32F7x MCU Selection"
+depends on SOC_SERIES_STM32F7X
+
+config SOC_STM32F723XE
+	bool "STM32F723XE"
+
+config SOC_STM32F746XG
+	bool "STM32F746XG"
+
+config SOC_STM32F769XI
+	bool "STM32F769XI"
+
+endchoice