ixgbe: fix build error with FCOE_CONFIG without DCB_CONFIG

Building ixgbe without DCB_CONFIG and FCOE_CONFIG will cause
a build error.  This resolves the build error by wrapping
the fcoe.up in CONFIG_IXGBE_DCB ifdefs.

Also frames were being priority VLAN tagged even without DCB
enabled.  This fixes this so that 8021Q priority tags are
only added with DCB actually enabled.

Reported-by: divya <dipraksh@linux.vnet.ibm.com>
Reported-by: Jon Mason <jon.mason@exar.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>