Update swd-pi.cmd to support Pi 1 with 26 pin GPIO header

[geoffrey-vl]

For old Pi 1 a/b with 26 pin GPIO header we need different bit-banging IO.
Tested it, its working for removing flash protection from PineTime using Raspberry Pi 1 B rev1.2.

[lupyuen]

Hi: Thanks for the PR. Sorry this repo has been superseded by this...

https://github.com/lupyuen/pinetime-rust-mynewt

Can you check whether the new repo has the same problem? Thanks!

[geoffrey-vl]

Hi, I ended up here through one of your web tutorials, and only needed this particular file from your entire repo. I haven't really looked at anything else in this repo to be honest, just this particular file. Anyway, if this repo is no longer to be used please "archive", and link to your newer work. I had a quick look into your new repo, but it seems you've refactored some stuff and I'm not really willing to spend much time into finding out how to apply the patch on your newer work.
Anyway, the patch did if for me, I only wanted to share that experience so feel free to merge that (or not)