net: phy: realtek: add RTL8125D-internal PHY

The first boards show up with Realtek's RTL8125D. This MAC/PHY chip
comes with an integrated 2.5Gbps PHY with ID 0x001cc841. It's not
clear yet whether there's an external version of this PHY and how
Realtek calls it, therefore use the numeric id for now.

Link: https://lore.kernel.org/netdev/2ada65e1-5dfa-456c-9334-2bc51272e9da@gmail.com/T/


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Message-ID: <7d2924de-053b-44d2-a479-870dc3878170@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>