pkg/uwb-dw1000: fix default group delay, use OTP values when possible

[fjmolinas]

Contribution description

This PR fixed the default values for the transmitter calibration block group delay. It seems that when I ported this I set the default group delay to the wrong value of 5 or (DW1000_CHANNEL_DEFAULT), when the actual correct value for the default channel 5 is 0xC0. This fixes it.

Furthermore, by playing with the default firmware decawave provides its boards with there is also calibrated TX_POWER and PG_DELAY values stored in the OTP memory (at least for channel 5). These values are calibrated to account for fabrication process variation in antenna gains among others and therefore be sure that the output TX power is according to regulations, so use them when they are available.

A couple of cleanups are piggy-packed int his PR, mainly to reduce CI builds.

Testing procedure

Bench results of twr_aloha against master, a notable improvement should be visible, running on IoT-LAB and evaluating the mean error over 14nodes I get:

          count      mean       std       min       25%       50%       75%       max
method                                                                               
deca    18185.0  0.084623  0.091720  0.000000  0.027582  0.060342  0.112198  0.967802
master  18192.0  0.194518  0.146984  0.000015  0.111583  0.173077  0.246428  6.866262
pr      18161.0  0.113226  0.120171  0.000004  0.040586  0.082905  0.150210  1.110259

Issues/PRs references

Split from #17988

[kaspar030]

Happy 18k everyone!!

[kaspar030]

ACK.

Code changes look fine. Provided testing indicates big improvements.

[fjmolinas]

Thanks!