ixgbe: Fix coexistence of FCoE and Flow Director in 82599

Fix coexistence of Fiber Channel over Ethernet (FCoE) and Flow Director (FDIR)
in 82599 and remove the disabling of FDIR when FCoE is enabled.

Currently, FDIR is turned off when FCoE is enabled under the assumption that
FCoE is always enabled with DCB being turned on. However, FDIR does not have
to be turned off all the time when FCoE is enabled since FCoE can be enabled
without DCB being turned on, e.g., use link pause only. This patch makes sure
that when DCB is turned on or off, FDIR is turned on or off correspondingly;
and when FCoE is enabled, it does not disable FDIR, rather, it will have FDIR
set up properly so FCoE and FDIR can coexist regardless of DCB being on or off.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>