drm/rockchip: vop: fix possible null-ptr-deref in vop_bind()

It will cause null-ptr-deref in resource_size(), if platform_get_resource()
returns NULL, move calling resource_size() after devm_ioremap_resource() that
will check 'res' to avoid null-ptr-deref.

Fixes: 2048e328 ("drm: rockchip: Add basic drm driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220422032854.2995175-1-yangyingliang@huawei.com

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -2118,10 +2118,10 @@ static int vop_bind(struct device *dev, struct device *master, void *data)
 	vop_win_init(vop);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	vop->len = resource_size(res);
 	vop->regs = devm_ioremap_resource(dev, res);
 	if (IS_ERR(vop->regs))
 		return PTR_ERR(vop->regs);
+	vop->len = resource_size(res);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 	if (res) {