Bluetooth: Controller: Add radio_sim_nrf54l.h file

Add radio_sim_nrf54l.h file, which for now a copy of the
SoC radio_nrf54lx.h file. This is added for having separate
simulation model dependent timing values and specific
implementation details.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>