stm32: move stm32 specific code to mach-stm32

This patch moves stm32 sources at one place, with this armv7m now contains
only generic stuff.

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
diff --git a/arch/arm/mach-stm32/stm32f4/Kconfig b/arch/arm/mach-stm32/stm32f4/Kconfig
new file mode 100644
index 0000000..a63619e
--- /dev/null
+++ b/arch/arm/mach-stm32/stm32f4/Kconfig
@@ -0,0 +1,8 @@
+if STM32F4
+
+config TARGET_STM32F429_DISCOVERY
+	bool "STM32F429 Discovery board"
+
+source "board/st/stm32f429-discovery/Kconfig"
+
+endif