Refactor InterpFilters variable

Replacing packed filter variable with union
for better readability.

Change-Id: I455e391d75826503cb8e34b01f5ee856ca8e2674
diff --git a/av1/encoder/block.h b/av1/encoder/block.h
index 1d1cbbe..35b4705 100644
--- a/av1/encoder/block.h
+++ b/av1/encoder/block.h
@@ -153,7 +153,7 @@
 
 #define MAX_INTERP_FILTER_STATS 64
 typedef struct {
-  InterpFilters filters;
+  int_interpfilters filters;
   int_mv mv[2];
   int8_t ref_frames[2];
   COMPOUND_TYPE comp_type;
@@ -171,7 +171,7 @@
   int_mv mv[2];
   MV_REFERENCE_FRAME ref_frames[2];
   PREDICTION_MODE mode;
-  InterpFilters filter;
+  int_interpfilters filter;
   int ref_mv_idx;
   int is_global[2];
 } COMP_RD_STATS;