Commit 8c4dfea9 ("nvme-fabrics: reject I/O to offline device")
introduced fast_io_fail_tmo but didn't export the value to sysfs. The
value can be set during the 'nvme connect'. Export the timeout value
to user space via sysfs to allow runtime configuration.

Cc: Victor Gladkov <Victor.Gladkov@kioxia.com>
Signed-off-by: NDaniel Wagner <dwagner@suse.de>
Reviewed-by: NEwan D. Milne <emilne@redhat.com>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NHimanshu Madhani <himanshu.madhaani@oracle.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>