[Ada] Simplify code for checks within an initialization procedure

[Pierre-Marie de Rodat via Gcc-patches]

It is simpler to access the type of first formal using semantic instead
of syntactic query. Behaviour is unaffected.

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

gcc/ada/

        * sem_util.adb (Compile_Time_Constraint_Error): Simplify getting
        the type of the first formal parameter.
diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -6590,9 +6590,7 @@ package body Sem_Util is
                if Inside_Init_Proc then
                   declare
                      Init_Proc_Type : constant Entity_Id :=
-                       Entity (Parameter_Type (First
-                                 (Parameter_Specifications
-                                    (Parent (Current_Scope_No_Loops)))));
+                       Etype (First_Formal (Current_Scope_No_Loops));
 
                      Conc_Typ : constant Entity_Id :=
                        (if Present (Init_Proc_Type)