bna: Delete get_flags and set_flags ethtool methods.

This driver doesn't support LRO, NTUPLE, or the RXHASH
features.  So it should not set these ethtool operations.

This also fixes the warning:

drivers/net/bna/bnad_ethtool.c:1272: warning: initialization from incompatible pointer type

Signed-off-by: David S. Miller <davem@davemloft.net>