net: airoha: Introduce airoha_irq_bank struct

net: airoha: Introduce airoha_irq_bank struct

EN7581 ethernet SoC supports 4 programmable IRQ lines each one composed
by 4 IRQ configuration registers. Add airoha_irq_bank struct as a
container for independent IRQ lines info (e.g. IRQ number, enabled source
interrupts, ecc). This is a preliminary patch to support multiple IRQ lines
in airoha_eth driver.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250418-airoha-eth-multi-irq-v1-1-1ab0083ca3c1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>