drm/panthor: unlock on error in panthor_ioctl_bo_create()

Call drm_dev_exit() before returning -EINVAL.

Fixes: cd2c9c3 ("drm/panthor: Add flag to map GEM object Write-Back Cacheable")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/aUOxxvXXtHHfFCcg@stanley.mountain
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Author: Dan Carpenter

drivers/gpu/drm/panthor/panthor_drv.c

@@ -923,8 +923,10 @@ static int panthor_ioctl_bo_create(struct drm_device *ddev, void *data,
 	}
 
 	if ((args->flags & DRM_PANTHOR_BO_NO_MMAP) &&
-	    (args->flags & DRM_PANTHOR_BO_WB_MMAP))
-		return -EINVAL;
+	    (args->flags & DRM_PANTHOR_BO_WB_MMAP)) {
+		ret = -EINVAL;
+		goto out_dev_exit;
+	}
 
 	if (args->exclusive_vm_id) {
 		vm = panthor_vm_pool_get_vm(pfile->vms, args->exclusive_vm_id);