net: phy: Add BaseT1 auto-negotiation registers

Added BASE-T1 AN advertisement register (Registers 7.514, 7.515, and
7.516) and BASE-T1 AN LP Base Page ability register (Registers 7.517,
7.518, and 7.519).

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>