drm/meson: dw-hdmi: Disable clocks on driver teardown

drm/meson: dw-hdmi: Disable clocks on driver teardown

[ Upstream commit 1dfeea904550c11eccf3fd5f6256e4b0f0208dfe ]

The HDMI driver request clocks early, but never disable them, leaving
the clocks on even when the driver is removed.

Fix it by slightly refactoring the clock code, and register a devm
action that will eventually disable/unprepare the enabled clocks.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201120094205.525228-2-maz@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>