An interrupt handler was added to the driver as well as functions
to enable interrupts at the phy.

There are several interrupts maskable at the phy, but only link change
interrupts are handled by the driver yet.
Signed-off-by: Andre Werner <andre.werner@systec-electronic.com>
Link: https://lore.kernel.org/r/20240129135734.18975-3-andre.werner@systec-electronic.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>