Remove redundant assignments of subsampling_x & y.

setup_buffer_pool() doesn't need to set the subsampling_x and
subsampling_y fields of pool->frame_bufs[cm->new_fb_idx].buf because the
aom_realloc_frame_buffer() call has already set those two fields to
seq_params->subsampling_x and seq_params->subsampling_y.

Change-Id: I2d9ccd041052e84c23745c5b058829d5dbb06ff3
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 2e96b60..b62c349 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -2379,10 +2379,6 @@
   }
   unlock_buffer_pool(pool);
 
-  pool->frame_bufs[cm->new_fb_idx].buf.subsampling_x =
-      seq_params->subsampling_x;
-  pool->frame_bufs[cm->new_fb_idx].buf.subsampling_y =
-      seq_params->subsampling_y;
   pool->frame_bufs[cm->new_fb_idx].buf.bit_depth =
       (unsigned int)seq_params->bit_depth;
   pool->frame_bufs[cm->new_fb_idx].buf.color_primaries =