[Ada] Refine type of a local variable

[Pierre-Marie de Rodat]

Formal parameters, while iterated with First_Formal/Next_Formal, are
entities and not just nodes.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * exp_ch6.adb (Is_Direct_Deep_Call): Refine type from Node_Id to
        Entity_Id.
diff --git a/gcc/ada/exp_ch6.adb b/gcc/ada/exp_ch6.adb
--- a/gcc/ada/exp_ch6.adb
+++ b/gcc/ada/exp_ch6.adb
@@ -3215,7 +3215,7 @@ package body Exp_Ch6 is
          then
             declare
                Actual : Node_Id;
-               Formal : Node_Id;
+               Formal : Entity_Id;
 
             begin
                Actual := First (Parameter_Associations (Call_Node));