be2net: implement ethtool set/get_channel hooks

Support is provided only for combined channels. When SR-IOV is not
enabled, BE3 supports upto 16 channels and Lancer-R/SH-R support upto
32 channels.

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