[SCSI] fcoe: have fcoe log off and lport destroy before ndo_fcoe_disable

Currently fcoe interface cleanup is done after ndo_fcoe_disable
and that prevents logoff going out to the peer, so this patch
moves all netdev cleanup and its releasing inside
fcoe_interface_cleanup to have log off before ndo_fcoe_disable
disables the fcoe.

This patch also fixes asymmetric rtnl locking around fcoe_if_destroy,
as currently this function requires rtnl held by its caller
and then have this func drops the lock, instead now don't have
any processing under rtnl inside fcoe_if_destroy, this required
moving few func to get build working again.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>