Don't define empty struct bsg_class_device if !CONFIG_BLK_DEV_BSG

Don't define empty struct bsg_class_device if !CONFIG_BLK_DEV_BSG

Don't define an empty struct bsg_class_device if !CONFIG_BLK_DEV_BSG.

It's embedded in struct request_queue, but there we have

#if defined(CONFIG_BLK_DEV_BSG)
	struct bsg_class_device bsg_dev;
#endif

anyway.

Signed-off-by: Geert Uytterhoeven <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>