drm/i915: Fix enabled infoframe states of lspcon

Compared to implementation of DP and HDMI's encoder->infoframes_enabled,
the lspcon's implementation returns its active state. (we expect enabled
infoframe states of HW.) It leads to pipe state mismatch error
when ddi_get_config is called.

Because the current implementation of lspcon is not ready to support
readout infoframes, we need to return 0 here.

In order to support readout to lspcon, we need to implement read_infoframe
and infoframes_enabled. And set_infoframes also have to set an appropriate
bit on crtc_state->infoframes.enable

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200514060732.3378396-11-gwan-gyeong.mun@intel.com

drivers/gpu/drm/i915/display/intel_lspcon.c

@@ -522,7 +522,7 @@ 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)->active;
+	return 0;
 }
 
 void lspcon_resume(struct intel_lspcon *lspcon)