[Ada] Fix typo in code to get a better error message

[Pierre-Marie de Rodat]

For illegal name of a generic unit in a USE clause we tailor the message
based on the kind of the generic, but we failed to detect generic
procedures.

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

gcc/ada/

        * sem_ch8.adb (Analyze_Use_Package): Replace low-level,
        error-prone Ekind_In tests with high-level Is_Generic_Subprogram
        and Is_Subprogram.
diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb
--- a/gcc/ada/sem_ch8.adb
+++ b/gcc/ada/sem_ch8.adb
@@ -3981,20 +3981,19 @@ package body Sem_Ch8 is
          Set_Prev_Use_Clause (N, Current_Use_Clause (Pack));
       end if;
 
-      --  Mark all entities as potentially use visible.
+      --  Mark all entities as potentially use visible
 
       if Ekind (Pack) /= E_Package and then Etype (Pack) /= Any_Type then
          if Ekind (Pack) = E_Generic_Package then
             Error_Msg_N  -- CODEFIX
               ("a generic package is not allowed in a use clause", Name (N));
 
-         elsif Ekind_In (Pack, E_Generic_Function, E_Generic_Package)
-         then
+         elsif Is_Generic_Subprogram (Pack) then
             Error_Msg_N  -- CODEFIX
               ("a generic subprogram is not allowed in a use clause",
                Name (N));
 
-         elsif Ekind_In (Pack, E_Function, E_Procedure, E_Operator) then
+         elsif Is_Subprogram (Pack) then
             Error_Msg_N  -- CODEFIX
               ("a subprogram is not allowed in a use clause", Name (N));