Bluetooth: ISO: Support SCM_TIMESTAMPING for ISO TS

User-space applications (e.g. PipeWire) depend on
ISO-formatted timestamps for precise audio sync.

The ISO ts is based on the controller’s clock domain,
so hardware timestamping (hwtimestamp) must be used.

Ref: Documentation/networking/timestamping.rst,
section 3.1 Hardware Timestamping.

Signed-off-by: Yang Li <yang.li@amlogic.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>