net: phy: realtek: add defines for shadowed c45 standard registers

Realtek shadows standard c45 registers in VEND2 device register space.
Add defines for these VEND2 registers, based on the names of the
standard c45 registers.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/c90bdf76-f8b8-4d06-9656-7a52d5658ee6@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>