drm/i915: Constify intel_drrs_init() args

Pass the fixed_mode as const to intel_drrs_init() since it's
not supposed to mutate the mode.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220310004802.16310-3-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -421,7 +421,7 @@ void intel_drrs_page_flip(struct intel_atomic_state *state,
  */
 struct drm_display_mode *
 intel_drrs_init(struct intel_connector *connector,
-		struct drm_display_mode *fixed_mode)
+		const struct drm_display_mode *fixed_mode)
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
 	struct intel_encoder *encoder = connector->encoder;

drivers/gpu/drm/i915/display/intel_drrs.h

@@ -31,6 +31,6 @@ void intel_drrs_compute_config(struct intel_dp *intel_dp,
 			       struct intel_crtc_state *pipe_config,
 			       int output_bpp, bool constant_n);
 struct drm_display_mode *intel_drrs_init(struct intel_connector *connector,
-					 struct drm_display_mode *fixed_mode);
+					 const struct drm_display_mode *fixed_mode);
 
 #endif /* __INTEL_DRRS_H__ */