kernel - Reduce ig4 receive errors

kernel - Reduce ig4 receive errors

* The timeout code now checks the FIFO and register status at least once
  before testing whether the timeout has been exceeded, and at least once
  more after waiting the timeout period.

  Previously the code would check, see that no data was present, then delay
  a little and check whether a timeout occurred after the delay without
  again testing whether data is present.

* Appears to fix receive timeouts reported by cyapa and atmel_mxt.