net: phy: lan87xx: use genphy_read_master_slave in read_status

To read the master slave configuration of the LAN87xx T1 phy, used the
generic phy driver genphy_read_master_slave function. Removed the local
lan87xx_read_master_slave function.

Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>