drm/i915: Precompute HDMI infoframes

Store the infoframes in the crtc state and precompute them in
.compute_config(). While precomputing we'll also fill out the
inforames.enable bitmask appropriately.

v2: Drop the null packet stuff (Daniel)
    Add a FIXME for lspcon
v3: .compute_config() now returns int

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/20190225174106.2163-5-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/intel_lspcon.c

@@ -470,6 +470,8 @@ void lspcon_set_infoframes(struct intel_encoder *encoder,
 		return;
 	}
 
+	/* FIXME precompute infoframes */
+
 	ret = drm_hdmi_avi_infoframe_from_display_mode(&frame.avi,
 						       conn_state->connector,
 						       adjusted_mode);