net: thunderx: Add receive error stats reporting via ethtool

Added ethtool support to dump receive packet error statistics reported
in CQE. Also made some small fixes

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: Aleksey Makarov <aleksey.makarov@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>