net/i40e/base: add function to get FW LLDP agent status

net/i40e/base: add function to get FW LLDP agent status

This change introduces i40e_get_fw_lldp_status() function capable of
reporting status of FW Link Layer Discovery Protocol (LLDP) agent.

Since reading LLDP configuration from NVM only gives information what
is the default state of FW LLDP agent after POR, this change introduces
more reliable method for checking if agent is enabled.

Current state of FW LLDP agent may be different if user disabled the
agent, so i40e_get_fw_lldp_status() uses LLDP MIB checking to determine
status of the agent.

Signed-off-by: Piotr Pietruszewski <piotr.pietruszewski@intel.com>
Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>