drm/vgem: Fix vgem_init to get drm device available.

Modify vgem_init to take platform dev as parent in drm_dev_init.
This will make drm device available at "/sys/devices/platform/vgem"
in x86 chromebook.

v2: rebase, address checkpatch typo and line over 80 characters

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Deepak Sharma <deepak.sharma@amd.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023163550.15211-1-emil.l.velikov@gmail.com

drivers/gpu/drm/vgem/vgem_drv.c

@@ -471,31 +471,31 @@ static int __init vgem_init(void)
 	if (!vgem_device)
 		return -ENOMEM;
 
-	ret = drm_dev_init(&vgem_device->drm, &vgem_driver, NULL);
-	if (ret)
-		goto out_free;
-
 	vgem_device->platform =
 		platform_device_register_simple("vgem", -1, NULL, 0);
 	if (IS_ERR(vgem_device->platform)) {
 		ret = PTR_ERR(vgem_device->platform);
-		goto out_fini;
+		goto out_free;
 	}
 
 	dma_coerce_mask_and_coherent(&vgem_device->platform->dev,
 				     DMA_BIT_MASK(64));
+	ret = drm_dev_init(&vgem_device->drm, &vgem_driver,
+			   &vgem_device->platform->dev);
+	if (ret)
+		goto out_unregister;
 
 	/* Final step: expose the device/driver to userspace */
 	ret  = drm_dev_register(&vgem_device->drm, 0);
 	if (ret)
-		goto out_unregister;
+		goto out_fini;
 
 	return 0;
 
-out_unregister:
-	platform_device_unregister(vgem_device->platform);
 out_fini:
 	drm_dev_fini(&vgem_device->drm);
+out_unregister:
+	platform_device_unregister(vgem_device->platform);
 out_free:
 	kfree(vgem_device);
 	return ret;