Add comments about order of close ops

Per suggestion of @awlauria, added some comments about
the need to free ep before resources it points to.

Signed-off-by: Harumi Kuno <harumi.kuno@hpe.com>

opal/mca/btl/ofi/btl_ofi_component.c

@@ -581,6 +581,7 @@ static int mca_btl_ofi_init_device(struct fi_info *info)
 fail:
     /* clean up */
 
+    /* close basic ep before closing av */
     if (NULL != ep && !module->is_scalable_ep) {
         fi_close(&ep->fid);
     }
@@ -592,10 +593,12 @@ fail:
     }
     free(module->contexts);
 
+    /* check for NULL ep to avoid double-close */
     if (NULL != ep) {
         fi_close(&ep->fid);
     }
 
+    /* close av after closing basic ep */
     if (NULL != av) {
         fi_close(&av->fid);
     }

opal/mca/btl/ofi/btl_ofi_module.c

@@ -283,7 +283,7 @@ int mca_btl_ofi_finalize (mca_btl_base_module_t* btl)
         ofi_btl->rcache = NULL;
     }
 
-    /* For a standard ep, we need to close the ep first. */
+    /* Close basic ep before closing its attached resources. */
     if (NULL != ofi_btl->ofi_endpoint && !ofi_btl->is_scalable_ep) {
         fi_close(&ofi_btl->ofi_endpoint->fid);
         ofi_btl->ofi_endpoint = NULL;
@@ -299,6 +299,7 @@ int mca_btl_ofi_finalize (mca_btl_base_module_t* btl)
         fi_close(&ofi_btl->ofi_endpoint->fid);
     }
 
+    /* close ep before closing av */
     if (NULL != ofi_btl->av) {
         fi_close(&ofi_btl->av->fid);
     }