Let is_interp_needed always return 1

This CL will cause
0.122% PSNR drop on lowres dataset
0.059% PSNR drop on midres dataset

However, it will facilitate hardware implementation.

Change-Id: I0a0713acacbfd571509a721337711c021915dd3c
diff --git a/av1/common/reconinter.h b/av1/common/reconinter.h
index 5082d7b..d3863ee 100644
--- a/av1/common/reconinter.h
+++ b/av1/common/reconinter.h
@@ -460,7 +460,9 @@
   return 0;
 }
 
+#define CHECK_SUBPEL 0
 static INLINE int av1_is_interp_needed(const MACROBLOCKD *const xd) {
+#if CHECK_SUBPEL
   MODE_INFO *const mi = xd->mi[0];
   const int is_compound = has_second_ref(&mi->mbmi);
   int ref;
@@ -474,6 +476,10 @@
     }
   }
   return 0;
+#else
+  (void)xd;
+  return 1;
+#endif
 }
 
 #if CONFIG_MOTION_VAR