Fix clear keyframes op not reporting when called over a locked fcurve.

Debug print here is not that useful to common user, and keyframe deletion
does report warning, so do the same for clear op.

Reported by venomgfx over IRC, thanks.

source/blender/editors/animation/keyframing.c

@@ -1253,8 +1253,9 @@ static short clear_keyframe(ReportList *reports, ID *id, bAction *act, const cha
 			continue;
 
 		if (BKE_fcurve_is_protected(fcu)) {
-			if (G.debug & G_DEBUG)
-				printf("WARNING: not deleting keyframe for locked F-Curve\n");
+			BKE_reportf(reports, RPT_WARNING,
+			            "Not clearing all keyframes from locked F-Curve '%s' for %s '%s'",
+			            fcu->rna_path, BKE_idcode_to_name(GS(id->name)), id->name + 2);
 			continue;
 		}