btl/scif: use safe syntax

PGI compilers 2013 and older do not support the following syntax :
mca_btl_scif_modex_t modex = {.port_id = mca_btl_scif_module.port_id};
so split it on two lines

cmr=v1.8.2:reviewer=hjelmn

This commit was SVN r32555.

opal/mca/btl/scif/btl_scif_component.c

@@ -208,7 +208,8 @@ static void mca_btl_scif_autoset_leave_pinned (void) {
 
 static int mca_btl_scif_modex_send (void)
 {
-    mca_btl_scif_modex_t modex = {.port_id = mca_btl_scif_module.port_id};
+    mca_btl_scif_modex_t modex;
+    modex.port_id = mca_btl_scif_module.port_id;
 
     return opal_modex_send (&mca_btl_scif_component.super.btl_version, &modex, sizeof (modex));
 }