ARM: stm32: create dedicated kconfig for STM32 machine

Create a dedicated Kconfig file in mach-stm32/ and move existing stm32
configs inside.
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>

arch/arm/Kconfig

@@ -819,6 +819,8 @@ source "arch/arm/mach-spear/Kconfig"
 
 source "arch/arm/mach-sti/Kconfig"
 
+source "arch/arm/mach-stm32/Kconfig"
+
 source "arch/arm/mach-s3c24xx/Kconfig"
 
 source "arch/arm/mach-s3c64xx/Kconfig"
@@ -877,28 +879,6 @@ config ARCH_LPC18XX
 	  Support for NXP's LPC18xx Cortex-M3 and LPC43xx Cortex-M4
 	  high performance microcontrollers.
 
-config ARCH_STM32
-	bool "STMicrolectronics STM32"
-	depends on ARM_SINGLE_ARMV7M
-	select ARCH_HAS_RESET_CONTROLLER
-	select ARMV7M_SYSTICK
-	select CLKSRC_STM32
-	select PINCTRL
-	select RESET_CONTROLLER
-	select STM32_EXTI
-	help
-	  Support for STMicroelectronics STM32 processors.
-
-config MACH_STM32F429
-	bool "STMicrolectronics STM32F429"
-	depends on ARCH_STM32
-	default y
-
-config MACH_STM32F746
-	bool "STMicrolectronics STM32F746"
-	depends on ARCH_STM32
-	default y
-
 config ARCH_MPS2
 	bool "ARM MPS2 platform"
 	depends on ARM_SINGLE_ARMV7M

arch/arm/mach-stm32/Kconfig

+config ARCH_STM32
+	bool "STMicrolectronics STM32"
+	depends on ARM_SINGLE_ARMV7M
+	select ARCH_HAS_RESET_CONTROLLER
+	select ARMV7M_SYSTICK
+	select CLKSRC_STM32
+	select PINCTRL
+	select RESET_CONTROLLER
+	select STM32_EXTI
+	help
+	  Support for STMicroelectronics STM32 processors.
+
+config MACH_STM32F429
+	bool "STMicrolectronics STM32F429"
+	depends on ARCH_STM32
+	default y
+
+config MACH_STM32F746
+	bool "STMicrolectronics STM32F746"
+	depends on ARCH_STM32
+	default y