ceph: fix alignment of rasize

[ Upstream commit c36ed50de2ad1649ce0369a4a6fc2cc11b20dfb7 ]

On currently logic:
when I specify rasize=0~1 then it will be 4096.
when I specify rasize=2~4097 then it will be 8192.

Make it the same as rsize & wsize.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>