net: phy: realtek: add interrupt support for RTL8221B

net: phy: realtek: add interrupt support for RTL8221B

This commit introduces interrupt support for RTL8221B (C45 mode).
Interrupts are mapped on the VEND2 page. VEND2 registers are only
accessible via C45 reads and cannot be accessed by C45 over C22.

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>
[Enable only link state change interrupts]
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251102152644.1676482-1-olek2@wp.pl
Signed-off-by: Jakub Kicinski <kuba@kernel.org>