Remove Half duplex mode speed capabilities.

Since Half Duplex mode has been deprecated by the firmware, driver should
not advertise Half Duplex speed in ethtool support link speed values.

Fixes: 071a0204 ("net: atlantic: A2: half duplex support")
Signed-off-by: Sameer Saurabh <ssaurabh@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>