s/INTERP_FILTER/InterpFilter/

this matches style guidelines and stabilizes successive runs of
clang-format across the tree. remaining types should be address in
successive commits.

Change-Id: I6ad3f69cf0a22cb9a9b895b272195f891f71170f

av1/encoder/encoder.c

@@ -4429,7 +4429,7 @@ static void set_arf_sign_bias(AV1_COMP *cpi) {
 }
 
 static int setup_interp_filter_search_mask(AV1_COMP *cpi) {
-  INTERP_FILTER ifilter;
+  InterpFilter ifilter;
   int ref_total[TOTAL_REFS_PER_FRAME] = { 0 };
   MV_REFERENCE_FRAME ref;
   int mask = 0;