stlink: replace odr register for the isol variant

[HrMitrev]

Detailed description

This is a follow up to PR1720 where I used the Output Data Register of the GPIO peripheral, causing read modify write. Now we use BSRR and BRR which only require a single write. I benchmarked the speed(when flashing 128kb firmware file) of the probe after this patch and it seems to be very similar, however the code size is reduced by a few bytes and as we know - every byte counts

• I've read the Code of Conduct
• I've read the guidelines for contributing to this repository
• It builds for hardware native (make PROBE_HOST=native)
• It builds as BMDA (make PROBE_HOST=hosted)
• I've tested it to the best of my ability
• My commit messages provide a useful short description of what the commits do

Closing issues

N/A

[dragonmux]

There's only one review item we have - with it addressed, this LGTM and can be merged.

[dragonmux]

LGTM, merging - thank you for the contribution!