drivers/net/phy: add the link modes for the 10BASE-T1S Ethernet PHY

This patch adds the link modes for the IEEE 802.3cg Clause 147 10BASE-T1S
Ethernet PHY. According to the specifications, the 10BASE-T1S supports
Point-To-Point Full-Duplex, Point-To-Point Half-Duplex and/or
Point-To-Multipoint (AKA Multi-Drop) Half-Duplex operations.

Signed-off-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>