When checking link status during a hot plug event or detecting sink
presence, we need to retry 3 times per the spec (section 9.1 of the 1.1a
DisplayPort spec).  Consolidate the retry code into a
native_aux_read_retry function for use by get_link_status and _detect.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NKeith Packard <keithp@keithp.com>