drm/ast: Remove vga2_clone field

Remove the unused field vga2_clone from struct ast_device. No
functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Jocelyn Falempe <jfalempe@redhat.com> # AST2600
Link: https://patchwork.freedesktop.org/patch/msgid/20230621130032.3568-3-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_drv.h

@@ -166,7 +166,6 @@ struct ast_device {
 	void __iomem *dp501_fw_buf;
 
 	enum ast_chip chip;
-	bool vga2_clone;
 	uint32_t dram_bus_width;
 	uint32_t dram_type;
 	uint32_t mclk;

drivers/gpu/drm/ast/ast_main.c

@@ -179,7 +179,6 @@ static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 			drm_info(dev, "AST 2100 detected\n");
 			break;
 		}
-		ast->vga2_clone = false;
 	} else {
 		ast->chip = AST2000;
 		drm_info(dev, "AST 2000 detected\n");