ch4: fix unused variable warning

A left-over unused assignment.

Author: hzhou

src/mpid/ch4/src/ch4_send.h

@@ -24,8 +24,7 @@ MPL_STATIC_INLINE_PREFIX int MPIDI_isend(const void *buf,
 #ifdef MPIDI_CH4_DIRECT_NETMOD
     mpi_errno = MPIDI_NM_mpi_isend(buf, count, datatype, rank, tag, comm, attr, av, req);
 #else
-    int r;
-    if ((r = MPIDI_av_is_local(av)))
+    if ((MPIDI_av_is_local(av)))
         mpi_errno = MPIDI_SHM_mpi_isend(buf, count, datatype, rank, tag, comm, attr, av, req);
     else
         mpi_errno = MPIDI_NM_mpi_isend(buf, count, datatype, rank, tag, comm, attr, av, req);