drm/i915/hdmi: fetch infoframe status in get_config v2

This is useful for checking things later.

v2:
  - fix hsw infoframe enabled check (Ander)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
[danvet: Add the missing PIPE_CONF_CHECK_I(has_infoframe); line to the
hw state cross-checker.]
[danet: Squash in fixup from Jesse to correctly compute has_infoframe
in the hdmi compute_config function.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>