Demonstrations for ADC operation.

Prepare requirements:
(1)PA5 connects to slide rheostat, external voltage supply, temperature sensor, etc.

1. ADC_Single_Rigesters_Ebus_Demo:
   Tim8 generate event 0 and event 1 to trigger ADC_CHANNEL_5 to sample and convert PA5's
   input, after converted, will inform APP by interrupt event.

2. ADC_Double_Rigesters_Ebus_Demo
   Tim8 generate TRGO event to trigger ADC_CHANNEL_5 and ADC_CHANNEL_6 to
   sample, after converted, will inform APP by interrupt event.
