wil6210: platform hooks for modile init/exit

Provide platform hooks for module init/exit.
If platform require to perform some specific actions
in global context, this is where to do so.

Example may be turning on power for the PCIE based
on DT information.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>