Fix checking address on I2C transaction start/end

[eldruin]

I have noticed that the addresses supplied in the transaction start/end are not checked. Hence this PR.
Although I am wondering now if the transaction start/end should have an address parameter at all. Maybe we should remove it altogether.

[dbrgn]

Although I am wondering now if the transaction start/end should have an address parameter at all. Maybe we should remove it altogether.

How would you pass the address argument to the read/write functions in that case?

[eldruin]

The address is already checked in the individual steps.

[ I2cTrans::transaction_start(ADDR),
  I2cTrans::write(ADDR, vec![0]),
  I2cTrans::read(ADDR, &mut data),
  I2cTrans::transaction_end(ADDR) ]

vs.

[ I2cTrans::transaction_start(),
  I2cTrans::write(ADDR, vec![0]),
  I2cTrans::read(ADDR, &mut data),
  I2cTrans::transaction_end() ]

[asasine]

Removing the address from the transaction start is opposite to how the underlying bus works for multiple operations. The address is sent as part of start/repeated start, and not as part of the write/read operations. If anything, the address should be only included in the starts and removed from everything else.