net/i40e/base: read LPI status from external PHY

net/i40e/base: read LPI status from external PHY

When external PHY is used, MAC register may not reflect actual
state of LPI. Add function reading it directly from PHY or MAC,
depending on what is supported by the device.

Signed-off-by: Krzysztof Galazka <krzysztof.galazka@intel.com>
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>