rc: no need to strdup the value returned by var_GetString.

(cherry picked from commit a9aa82f3)
Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

modules/control/rc.c

@@ -1750,7 +1750,7 @@ static int VideoConfig( vlc_object_t *p_this, char const *psz_cmd,
         }
         else
         {
-            psz_value = strdup( val.psz_string );
+            psz_value = val.psz_string;
         }
 
         if ( var_Change( p_vout, psz_variable,