drm/i915: Return the mask of enabled infoframes from ->inforame_enabled()

We want to start tracking which infoframes are enabled, so let's replace
the boolean flag with a bitmask.

We'll abstract the bitmask so that it's not platform dependent. That
will allow us to examine the bitmask later in platform independent code.

v2: Don't map VIDEO_DIP_ENABLE to the null packet (Daniel)
    Put a FIXME in the lspcon function

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190225174106.2163-3-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/intel_lspcon.c

@@ -504,9 +504,10 @@ void lspcon_set_infoframes(struct intel_encoder *encoder,
 				  buf, ret);
 }
 
-bool lspcon_infoframe_enabled(struct intel_encoder *encoder,
+u32 lspcon_infoframes_enabled(struct intel_encoder *encoder,
 			      const struct intel_crtc_state *pipe_config)
 {
+	/* FIXME actually read this from the hw */
 	return enc_to_intel_lspcon(&encoder->base)->active;
 }