[Ada] Remove double initialization of the known value cache

[Pierre-Marie de Rodat]

Global variable CV_Cache, where values known at compilation time are
stored, was initialization both by elaboration and by
Sem_Eval.Initialize, which is called from Gnatdrv1 and required by the
GNSA (GNAT Semantic Analyzer).

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

gcc/ada/

        * sem_eval.adb (CV_Cache): Remove initialization at elaboration.
diff --git a/gcc/ada/sem_eval.adb b/gcc/ada/sem_eval.adb
--- a/gcc/ada/sem_eval.adb
+++ b/gcc/ada/sem_eval.adb
@@ -124,7 +124,7 @@ package body Sem_Eval is
 
    type CV_Cache_Array is array (CV_Range) of CV_Entry;
 
-   CV_Cache : CV_Cache_Array := (others => (Node_High_Bound, Uint_0));
+   CV_Cache : CV_Cache_Array;
    --  This is the actual cache, with entries consisting of node/value pairs,
    --  and the impossible value Node_High_Bound used for unset entries.