drm/i915/lspcon: Do not send infoframes to non-HDMI sinks

Non-HDMI sinks shouldn't be sent infoframes. Check for that when
using LSPCON.

FIXME: How do we turn off infoframes once enabled? Do we even
       have to?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904115354.25336-3-ville.syrjala@linux.intel.com


Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>