net: thunderx: Fix link status reporting

Check for SMU RX local/remote faults along with SPU LINK
status. Otherwise at times link is UP at our end but DOWN
at link partner's side. Also due to an issue in BGX it's
rarely seen that initialization doesn't happen properly
and SMU RX reports faults with everything fine at SPU.
This patch tries to reinitialize LMAC to fix it.

Also fixed LMAC disable sequence to properly bring down link.

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: Tao Wang <tao.wang@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>