bnxt_en: Extend autoneg to all speeds.

Allow all autoneg speeds aupported by firmware to be advertised.  If
the advertising parameter is 0, then all supported speeds will be
advertised.

Remove BNXT_ALL_COPPER_ETHTOOL_SPEED which is no longer used as all
supported speeds can be advertised.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>