net: phy: microchip_t1: add lan87xx_phy_init to initialize the lan87xx phy.

lan87xx_phy_init() initializes the lan87xx phy hardware
including its TC10 Wake-up and Sleep features.

Fixes: 3e50d2da ("Add driver for Microchip LAN87XX T1 PHYs")
Signed-off-by: Yuiko Oshino <yuiko.oshino@microchip.com>
v0->v1:
    - Add more details in the commit message and source comments.
    - Update to the latest initialization sequences.
    - Add access_ereg_modify_changed().
    - Fix access_ereg() to access SMI bank correctly.
Signed-off-by: David S. Miller <davem@davemloft.net>