drm/bridge: anx7625: Make hpd workqueue freezable

There were still a race condition between hpd work and suspend, since
the workqueue work can still be run after anx7625 had powered off in
suspend.

Since we never want hpd work to run while suspending, and there's no
harm to delay them to be run after resume, mark the workqueue as
WQ_FREEZABLE so all works won't run while suspending.

Fixes: 409776fa ("drm/bridge: anx7625: add suspend / resume hooks")

Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210615032937.2328468-1-pihsun@chromium.org