drm/i915: Fix DP-MST crtc_mask

Each fake MST encoder is tied to a specific pipe. Fix the encoder's
crtc_mask to reflect that fact.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190817093902.2171-16-lucas.demarchi@intel.com

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

@@ -599,7 +599,7 @@ intel_dp_create_fake_mst_encoder(struct intel_digital_port *intel_dig_port, enum
 	intel_encoder->type = INTEL_OUTPUT_DP_MST;
 	intel_encoder->power_domain = intel_dig_port->base.power_domain;
 	intel_encoder->port = intel_dig_port->base.port;
-	intel_encoder->crtc_mask = 0x7;
+	intel_encoder->crtc_mask = BIT(pipe);
 	intel_encoder->cloneable = 0;
 
 	intel_encoder->compute_config = intel_dp_mst_compute_config;