Minor fixes to ADC code.
Minor fixes to ADC code.

openmv/openmv,kwagyeman/openmv,kwagyeman/openmv,kwagyeman/openmv,openmv/openmv,iabdalkader/openmv,iabdalkader/openmv,kwagyeman/openmv,iabdalkader/openmv,openmv/openmv,openmv/openmv,iabdalkader/openmv