[SCSI] libfc: update fc_host mfs along with updating lport->mfs

Currently fc_host mfs is not getting updated in
case its changed during FLOGI and that leaves fc_host
to show its initial old value in sysfs, so instead
have fc_host mfs updated along with updating lport mfs
during FLOGI.

Also in case of bad mfs during flogi, error out
instead of continuing with flogi.

[ Changes made by Robert Love: condition to '>=' and
  added printing of lport->mfs in DBG statement. FLOGI
  resp processing failed without being able to compare
  FCoE MFS 2112 against an incoming MFS of 2112 ]

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>