net: phy: adin: hook genphy_{suspend, resume} into the driver

The chip supports standard suspend/resume via BMCR reg.
Hook these functions into the `adin` driver.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>