x264: set b_vfr_input to 0, as it seems to matter now

I didn't observe any issues with 1.1 or 1.0.5 from file-input, but
lets just set it just in case when we have fps-value.

modules/codec/x264.c

@@ -1069,6 +1069,7 @@ static int  Open ( vlc_object_t *p_this )
     {
         p_sys->param.i_fps_num = p_enc->fmt_in.video.i_frame_rate;
         p_sys->param.i_fps_den = p_enc->fmt_in.video.i_frame_rate_base;
+        p_sys->param.b_vfr_input = 0;
     }
 
     /* Check slice-options */