IB/{nes, ipoib}: Pass supported flags to ethtool_op_set_flags()

Following commit 1437ce3983bcbc0447a0dedcd644c14fe833d266 "ethtool:
Change ethtool_op_set_flags to validate flags", ethtool_op_set_flags
takes a third parameter and cannot be used directly as an
implementation of ethtool_ops::set_flags.

Changes nes and ipoib driver to pass in the appropriate value.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>