Moving loopfilter struct to VP9_COMMON.

Loop filter configuration doesn't belong to macroblock, so moving it from
MACROBLOCKD to VP9_COMMON. Also moving the declaration of loopfilter struct
from vp9_blockd.h to vp9_loopfilter.h.

Change-Id: I4b3e34be9623b47cda35f9b1f9951f8c5b1d5d28

vp9/encoder/vp9_bitstream.c

@@ -1342,7 +1342,7 @@ static void write_uncompressed_header(VP9_COMP *cpi,
 
   vp9_wb_write_literal(wb, cm->frame_context_idx, NUM_FRAME_CONTEXTS_LOG2);
 
-  encode_loopfilter(&xd->lf, wb);
+  encode_loopfilter(&cm->lf, wb);
   encode_quantization(cm, wb);
   encode_segmentation(cpi, wb);