Errors flags could not clear making the i2c unusable after error.
This fix removes the error check in start so the error flags can clear and does proper checking for status bits before _bus_check.
- dont send stop if bus is busy and before any action is done on bus
- and bus check that looks for bus error, arbitration and nack events
- check for ACK (TXIS) before writing bytes on bus and not between each write
