mtl/psm: add missing header for opal_show_help

This commit was SVN r28146.

ompi/mca/mtl/psm/mtl_psm_component.c

@@ -24,6 +24,7 @@
 #include "opal/mca/event/event.h"
 #include "opal/util/output.h"
 #include "opal/mca/base/mca_base_param.h"
+#include "opal/util/show_help.h"
 #include "ompi/proc/proc.h"
 
 #include "mtl_psm.h"