nvme-fc: return non-zero status code when fails to create association

Return non-zero status code(-EIO) when needed, so re-connecting or
deleting controller will be triggered properly.

Signed-off-by: Michael Liang <mliang@purestorage.com>
Reviewed-by: Caleb Sander <csander@purestorage.com>
Reviewed-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>