drm: dw-hdmi-i2s: enable audio clock in audio_startup

drm: dw-hdmi-i2s: enable audio clock in audio_startup

In the designware databook, the sequence of enabling audio clock and
setting format is not clearly specified.
Currently, audio clock is enabled in the end of hw_param ops after
setting format.

On some monitors, there is a possibility that audio does not come out.
Fix this by enabling audio clock in audio_startup ops
before hw_param ops setting format.

Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190902035435.44463-1-cychiang@chromium.org