[platform][stm32f2xx] move ST's peripheral driver library into external/

external/platform/stm32f2xx/STM32F2xx_StdPeriph_Driver/rules.mk

@@ -1,5 +1,7 @@
 LOCAL_DIR := $(GET_LOCAL_DIR)
 
+MODULE := $(LOCAL_DIR)
+
 GLOBAL_INCLUDES += $(LOCAL_DIR)/inc
 
 MODULE_SRCS += \
@@ -35,3 +37,7 @@ MODULE_SRCS += \
 	$(LOCAL_DIR)/src/stm32f2xx_hash_sha1.c \
 	$(LOCAL_DIR)/src/stm32f2xx_cryp.c \
 	$(LOCAL_DIR)/src/stm32f2xx_dac.c \
+
+include $(LOCAL_DIR)/CMSIS/rules.mk
+
+include make/module.mk

platform/stm32f2xx/rules.mk

@@ -60,9 +60,8 @@ LINKER_SCRIPT += \
 	$(BUILDDIR)/system-twosegment.ld
 
 MODULE_DEPS += \
+	platform/stm32f2xx/STM32F2xx_StdPeriph_Driver \
 	arch/arm/arm-m/systick \
 	lib/cbuf
 
-include $(LOCAL_DIR)/STM32F2xx_StdPeriph_Driver/rules.mk $(LOCAL_DIR)/CMSIS/rules.mk
-
 include make/module.mk