19556: tools/mspdebug: fix `make debug` and `make debugserver` r=aabadie a=maribu
### Contribution description
The semantics of `make debug` and `make debugserver` have changed in the years since the MSP430 integration. This brings the implementation back into line with the current semantics
- `make debug` now starts both mspdebug and GDB, no need to run `make debugserver` prior to `make debug` anymore
- `make debug` no longer flashes the target to not waste flash erase cycles
- GDB mutliarch support is added
- support for selecting a debug adapter by its serial is added
19662: driver/lc709203f: remove unnecessary use of float r=aabadie a=kfessel
### Contribution description
removes a unnecessary use of float
### Testing procedure
read and test if you got that hardware (I don't)
### Issues/PRs references
#19614
Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Co-authored-by: Karl Fessel <karl.fessel@ovgu.de>
993c10a2a2