drm/ast: open key before detect chips

commit 8f372e25 upstream.

Some config settings like 3rd TX chips will not get correctly
if the extended reg is protected
Signed-off-by: Y.C. Chen <yc_chen@aspeedtech.com>
Reviewed-by: Egbert Eich <eich@suse.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/gpu/drm/ast/ast_main.c

@@ -66,6 +66,7 @@ uint8_t ast_get_index_reg_mask(struct ast_private *ast,
 static int ast_detect_chip(struct drm_device *dev)
 {
 	struct ast_private *ast = dev->dev_private;
+	ast_open_key(ast);
 
 	if (dev->pdev->device == PCI_CHIP_AST1180) {
 		ast->chip = AST1100;