Set use_highbitdepth flag to either 1 or 0

This reduces the buffer allocation size for high bit depth buffers by
more than 70%.

Change-Id: Iab9007d9684e8ac30ce7fa94e61f038f01792fc5

vp9/encoder/vp9_encoder.c

@@ -4141,7 +4141,7 @@ int vp9_receive_raw_frame(VP9_COMP *cpi, unsigned int frame_flags,
   const int subsampling_x = sd->subsampling_x;
   const int subsampling_y = sd->subsampling_y;
 #if CONFIG_VP9_HIGHBITDEPTH
-  const int use_highbitdepth = sd->flags & YV12_FLAG_HIGHBITDEPTH;
+  const int use_highbitdepth = (sd->flags & YV12_FLAG_HIGHBITDEPTH) != 0;
   check_initial_width(cpi, use_highbitdepth, subsampling_x, subsampling_y);
 #else
   check_initial_width(cpi, subsampling_x, subsampling_y);