ADC oversampling

[testo-jeff]

In function adc_mspm0_read_internal, need to map parameter oversampling from 0 ~ 8 to 0 ~ 128.

Because in applicaiton layer, this parapemter will be configed from 0 ~ 8 in sequence.

Please refer to adc_nrfx_saadc.c

[testo-jeff]

@parthitce Can you also please fix this minor issue as it is easy to fix so that we can close our internal bug.

[parthitce]

e8b9a27 addressed.