drm/meson: dw_hdmi: add resume/suspend hooks

Add the suspend and resume hooks to:
- reset the whole HDMI glue and HDMI controller on suspend
- re-init the HDMI glue and HDMI controller on resume

The HDMI glue init is refactored to be re-used from the resume hook.

It makes usage of dw_hdmi_resume() to recover a functionnal DDC bus.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Kevin Hilman <khilman@baylibre.com>
[narmstrong: fixed typo in commit log, and rebased on drm-misc-next]
Link: https://patchwork.freedesktop.org/patch/msgid/20190827095825.21015-2-narmstrong@baylibre.com