i40e: Check for LLDP AdminStatus before querying DCBX

This patch adds a check whether LLDP Agent's default AdminStatus is
enabled or disabled on a given port. If it is disabled then it sets
the DCBX status to disabled as well; and would not query firmware for
any DCBX configuration data.

Change-ID: I73c0b9f0adbf4cae177d14914b20a48c9a8f50fd
Signed-off-by: Neerav Parikh <neerav.parikh@intel.com>
Tested-By: Jack Morgan <jack.morgan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>