[modules] baro_bmp: remove obsolete warning
[stm32] fix adc and update update test

- very hack-ish fix for when using multiple ADs, e.g. AD1 and AD2
  Before this "fix" e.g. AD1_1 and AD2_1 had the same value (0).
- NB_ADC only needed for lpc21
- test_adc: send all raw ADC values

backport of #822