be2net: add speed reporting for 20G-KR interface

This patch adds speed reporting via ethtool for 20G KR2 interface on the
Skyhawk-R chip.

Signed-off-by: Vasundhara Volam <vasundhara.volam@emulex.com>
Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>