config: warning fixes

xf86AutoConfig.c: In function ‘FreeList’:
xf86AutoConfig.c:123: warning: passing argument 1 of ‘free’ discards
qualifiers from pointer target type
/usr/include/stdlib.h:488: note: expected ‘void *’ but argument is of
type ‘const char *’

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>

hw/xfree86/common/xf86AutoConfig.c

@@ -120,7 +120,7 @@ FreeList(const char ***list, int *lines)
     int i;
 
     for (i = 0; i < *lines; i++) {
-	free((*list)[i]);
+	free((char *)((*list)[i]));
     }
     free(*list);
     *list = NULL;