The driver didn't return with an error on (for example) a NACK on the
bus. This adds the expected error return. Due to the new case that a
transfer can be interrupted on an error, there were some new edge cases.
This patch therefore also fixes these edge cases by removing the
transfer_state that more or less duplicated the interrupt states.
Fixes#4591
Do some clean ups. Remove superfluous variables. Eliminate some overly
complex logic (information about transfer and remaining bytes has been
tracked redundantly in multiple variables).
This patch doesn't change the behavior of the driver.
Update #4591
