Rename "idle bus" to "bus available" per specification:
* Tune it to require < 1us.
Rename "IBI auto" to "IBI listen":
* Clarify that the controller is listening for IBI's:
* Explain that this field should be set.
* Fix for known IBI's DA with IBI disabled.
Signed-off-by: Jorge Marques <jorge.marques@analog.com>