[SCSI] fcoe: Call ndo_fcoe_enable/disable to turn FCoE feature on/off in LLD

Calls ndo_fcoe_enabled() of the associated netdev upon creating the FCoE
instance to make sure LLD has all necessary resources allocated and setup
properly before passing FCoE traffic. Similarly, calls ndo_fcoe_disable()
upon destroying the FCoE instance on the associated netdev to allow the LLD
to release all allocated resources for FCoE.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>