opaque_master: Add shutdown function in opaque_master struct

With this, register_opaque_master can take care of register_shutdown
as well, and every opaque master only needs to call
register_opaque_master instead of calling both register_opaque_master
and register_shutdown.

Next patches in the chain convert opaque masters to use new API.

Tested: builds and ninja test from CB:56413

Change-Id: I34183e6bafc787eec54ee4a26b73a40803f3ce99
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/56823
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72229
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed