drm/vc4: Use drm_hdmi_avi_infoframe_bars()

Use the new drm_hdmi_avi_infoframe_bars() helper instead
of hand rolling it.

Cc: Eric Anholt <eric@anholt.net>
Cc: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191008164814.5894-2-ville.syrjala@linux.intel.com
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>