bnxt_en: Add IPV6 hardware RFS support.

Accept ipv6 flows in .ndo_rx_flow_steer() and support ETHTOOL_GRXCLSRULE
ipv6 flows.

Signed-off-by: Michael Chan <michael.chan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>