Bluetooth: controller: corrected time-offset for endianness

Changes:
-- Corrected reading and writing time offset in framed segment header to
   account for endianness
-- Corrected bit positioning of time offset bit field in the segment
   header structure definition
-- Fixed upstream Zephyr BSIM test build failure due to debug logging
   39-bit variable

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