IOREG device: Implement system suspend callback

Add SIMPLE_DEV_PM_OPS callback to IOREG device in LWIS.
This change is major to avoid kernel panic because ISP were not
powered down before system suspend.

The suspend callback provide that is do clean up sequence
when system suspend is requested.

Bug: 185270350
Test: System suspend, GCA, CTS, camera checklist
Signed-off-by: Nick Chung <nickchung@google.com>
Change-Id: I86c7a0d73aa9f560188929d5cda38c3f93db8cbb