md/raid1: get rid of extra blank line and space

This patch get rid of extra blank line and space, and
add necessary space for code.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>