bsg: free the request before return error code

Free the request rq before returning error code.

Fixes: 972248e9 ("scsi: bsg-lib: handle bidi requests without block layer help")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>