[SCSI] libfcoe: eliminate unused link and last_link fields

The link and last_link fields in the fcoe_ctlr struct are no
longer useful, since they are always set to the same value,
and FIP always calls libfc to pass link information to the lport.

Eliminate those fields and rename link_work to timer_work, since
it no longer has any link change work to do.

Thanks to Brian Uchino for discovering this issue.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>