drm/ast: Call open_key before enable_mmio in POST code

open_key enables access the registers used by enable_mmio
Signed-off-by: NY.C. Chen <yc_chen@aspeedtech.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NJoel Stanley <joel@jms.id.au>
Tested-by: NY.C. Chen <yc_chen@aspeedtech.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/ast/ast_post.c

@@ -374,8 +374,8 @@ void ast_post_gpu(struct drm_device *dev)
 	pci_write_config_dword(ast->dev->pdev, 0x04, reg);
 
 	ast_enable_vga(dev);
-	ast_enable_mmio(dev);
 	ast_open_key(ast);
+	ast_enable_mmio(dev);
 	ast_set_def_ext_reg(dev);
 
 	if (ast->config_mode == ast_use_p2a) {