upd7810: Fixed ADC output register range.
upd7810: ADC functions should return bytes.
upd7810: sample and hold ADC value at start of conversion process.
upd7810: clear sample and hold on ADC reset
upd7810: remove code duplication in timers 0 and 1
upd7810: remove code duplication in ETIMER
upd7810: set ETIMER interrupts
Merge pull request #25 from ramiropolla/upd7810

upd7810: Some fixes and code simplification