net: phy: add qca8081 cdt feature

To perform CDT of qca8081 phy:
1. disable hibernation.
2. force phy working in MDI mode.
3. force phy working in 1000BASE-T mode.
4. configure the related thresholds.

Signed-off-by: Luo Jie <luoj@codeaurora.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>