[dfu] add dfu-util support to flash stm32

display in paparazzi center is still confusing. It seems the verbose
mode is not on stdout and the information status are red (dfuERROR status)
while they are not errors

conf/Makefile.stm32

@@ -231,17 +231,26 @@ $(AOBJ) : $(OBJDIR)/%.o : %.S
 # check which flash mode is configured
 #
 ifeq ($(FLASH_MODE),DFU)
+ifeq ($(DFU_UTIL),y)
+#
+# DFU flash mode using dfu-util
+DFU_ADDR ?= 0x08000000
+upload: $(OBJDIR)/$(TARGET).bin
+	@echo "Using dfu-util at $(DFU_ADDR)"
+	$(Q)dfu-util -d 0483:df11 -c 1 -i 0 -a 0 -s $(DFU_ADDR) -D $^ -v
+else
+#
+# DFU flash mode paparazzi stm32_mem
 ifdef DFU_ADDR
 DFU_ADDR_CMD = --addr=$(DFU_ADDR)
 endif
 ifdef DFU_PRODUCT
 DFU_PRODUCT_CMD = --product=$(DFU_PRODUCT)
 endif
-#
-# DFU flash mode
 upload: $(OBJDIR)/$(TARGET).bin
 	@echo "Using stm32 mem dfu loader"
 	$(PYTHON) $(PAPARAZZI_SRC)/sw/tools/dfu/stm32_mem.py $(DFU_PRODUCT_CMD) $(DFU_ADDR_CMD) $^
+endif
 
 #
 # serial flash mode

conf/boards/apogee_0.99.makefile

@@ -19,8 +19,9 @@ HARD_FLOAT=yes
 
 # default flash mode is via usb dfu bootloader
 # possibilities: DFU, SWD
-FLASH_MODE ?= SWD
+FLASH_MODE ?= DFU
 STLINK ?= y
+DFU_UTIL ?= y
 
 #
 # default LED configuration