src: lib: adc: Change to use max sample rate

[RaulTrombin]

Improoved the reading time of all 4 channels to 12ms instead previous 40ms.

• Issue: ADC Measuring time #54

read_adc                time:   [3.0672 ms 3.0759 ms 3.0840 ms]
                        change: [-69.244% -69.143% -69.034%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 23 outliers among 100 measurements (23.00%)
  17 (17.00%) low severe
  1 (1.00%) low mild
  4 (4.00%) high mild
  1 (1.00%) high severe

read_adc_all            time:   [12.350 ms 12.375 ms 12.409 ms]
                        change: [-69.174% -69.086% -68.976%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 23 outliers among 100 measurements (23.00%)
  14 (14.00%) low severe
  1 (1.00%) low mild
  3 (3.00%) high mild
  5 (5.00%) high severe