stmhal: Switch from dfu-util to tools/pydfu.py for deflt deploy method.

tools/pydfu.py is now the recommended way of deploying a DFU file.  Old
behaviour of dfu-util can be obtained by passing USE_PYDFU=0 when invoking
make.

The main README.md file has been updated to reflect this change.

README.md

@@ -130,7 +130,7 @@ The STM version
 
 The "stmhal" port requires an ARM compiler, arm-none-eabi-gcc, and associated
 bin-utils.  For those using Arch Linux, you need arm-none-eabi-binutils and
-arm-none-eabi-gcc packages from the AUR.  Otherwise, try here:
+arm-none-eabi-gcc packages.  Otherwise, try here:
 https://launchpad.net/gcc-arm-embedded
 
 To build:
@@ -146,9 +146,6 @@ Then to flash the code via USB DFU to your device:
 
     $ make deploy
 
-You will need the dfu-util program, on Arch Linux it's dfu-util-git in the
-AUR.  If the above does not work it may be because you don't have the
-correct permissions.  Try then:
-
-    $ sudo dfu-util -a 0 -d 0483:df11 -D build-PYBV10/firmware.dfu
-
+This will use the included `tools/pydfu.py` script.  If flashing the firmware
+does not work it may be because you don't have the correct permissions, and
+need to use `sudo make deploy`.

stmhal/Makefile

@@ -25,8 +25,8 @@ USBDEV_DIR=usbdev
 FATFS_DIR=lib/fatfs
 DFU=../tools/dfu.py
 # may need to prefix dfu-util with sudo
-USE_PYDFU ?= 0
-PYDFU = ../tools/pydfu.py
+USE_PYDFU ?= 1
+PYDFU ?= ../tools/pydfu.py
 DFU_UTIL ?= dfu-util
 DEVICE=0483:df11