header P4 pins numbered incorrectly in some documentation

[mossmann]

The ubertooth-dfu documentation (host/doc/man/ubertooth-dfu.1 and host/doc/ubertooth-dfu.md) incorrectly numbers the pins of header P4 on Ubertooth One and instructs users to connect pins 1 and 2 to activate DFU mode. If a user were to follow these instructions alone and were to not look at any other documentation, they would connect the correct pins, but the pin identified as pin 2 is in fact pin 3.

Pins 1 and 3 are correctly identified in firmware/bootloader/README as the pins to be connected. This agrees with the numbering in the hardware design files, the firmware source code, and the diagram web/content/images/u1_roadmap.png.

[mossmann]

I just corrected this on the wiki. One wiki page had it wrong while another had it right.

[mossmann]

A photo like this one would be nice in the documentation: https://user-images.githubusercontent.com/43299354/46984794-0c5ed680-d0b5-11e8-928e-58238d224efe.jpg