RDMA/hns: fix spelling mistake "attatch" -> "attach"

There is a spelling mistake in an error message. Fix it.

Link: https://lore.kernel.org/r/20200304081045.81164-1-colin.king@canonical.com


Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>