Unify the void cast usage

1.Remove void cast for function because many place ignore the returned value witout cast
2.Replace void cast for variable with UNUSED macro

Change-Id: Ie644129a563244a6397036789c4c3ea83c4e9b09
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

nshlib/nsh_modcmds.c

@@ -181,7 +181,7 @@ int cmd_lsmod(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
                  datasize      ? datasize      : "");
     }
 
-  (void)fclose(stream);
+  fclose(stream);
   return OK;
 }
 #endif /* CONFIG_FS_PROCFS && !CONFIG_FS_PROCFS_EXCLUDE_MODULE */