Bluetooth: Controller: Dispatch rx nodes for sync immediately

Periodic advertising reports can be reated directly from single PDU
as they do not require any information from superior PDU, so we can
dispatch them immediately instead of buffering in aux context and
flushing at the end of chain.

This also resolves proper order of Periodic advertising and IQ reports.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>