port: do not send sync and announce messages when dds.priority1 == 255 (slave only)

Signed-off-by: Delio Brignoli <dbrignoli@audioscience.com>
clock: increment gmTimeBaseIndicator every time we become master

Signed-off-by: Delio Brignoli <dbrignoli@audioscience.com>
Merge remote-tracking branch 'origin/asi1230-upstream-tracking' into asi1230-master