Bluetooth: Controller: ISO-AL validation and selection of TX time stamps

Intent is to pass Ellisys ISOAL quality tests for framed TX scenarios
where the TX SDU includes a time stamp that is not based on the
controller's clock.

Changes:
-- Include controller's reception time as a separate field in the TX SDU
   information
-- Include decision on whether SDU time stamp is valid and based on the
   controller's clock
-- Arbitrate and select / compute time stamp for the SDU

Signed-off-by: Nirosharn Amarasinghe <niag@demant.com>