Add more hints when troubleshooting panda (commaai#864)

* Add more hints when troubleshooting panda

* mention different command for panda red
* mention panda paw

* Update board/README.md

* Apply suggestions from code review

Co-authored-by: Adeeb Shihadeh <adeebshihadeh@gmail.com>

board/README.md

@@ -21,17 +21,21 @@ Programming
 **Panda**
 
 ```
-scons -u # Compile
-./flash.sh # Compile & Flash
+scons -u       # Compile
+./flash_h7.sh  # for red panda
+./flash.sh     # for other pandas
 ```
 
 Troubleshooting
 ----
 
 If your panda will not flash and is quickly blinking a single Green LED, use:
 ```
-./recover.sh
+./recover_h7.sh  # for red panda
+./recover.sh     # for other pandas
 ```
 
+A [panda paw](https://comma.ai/shop/products/panda-paw) can be used to put panda into DFU mode.
+
 
 [dfu-util](http://github.com/dsigma/dfu-util.git) for flashing