opal/mca/pmix: include opal_list.h in pmix_internal.h

"opal_list.h" happens to be included by "tsd.h" in mca/threads when a
thread type is POSIX, but "mca/threads/threads.h" of other thread types
do indirectly not include tsd.h and thus no "opal_list.h".

"pmix_internal.h" directly uses opal_list_item_t and thus should include
"opal_list.h" in its header.

Signed-off-by: Shintaro Iwasaki <siwasaki@anl.gov>

Author: shintaro-iwasaki

opal/mca/pmix/pmix-internal.h

@@ -10,6 +10,8 @@
  * Copyright (c) 2020      Amazon.com, Inc. or its affiliates.
  *                         All Rights reserved.
  * Copyright (c) 2021      Nanook Consulting.  All rights reserved.
+ * Copyright (c) 2021      Argonne National Laboratory.  All rights
+ *                         reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -37,6 +39,7 @@
 
 #include "opal/hash_string.h"
 #include "opal/mca/mca.h"
+#include "opal/class/opal_list.h"
 #include "opal/mca/threads/threads.h"
 #include "opal/util/error.h"
 #include "opal/util/event.h"