net: ethernet: mtk_eth_soc: skip first IRQ if not used

net: ethernet: mtk_eth_soc: skip first IRQ if not used

On SoCs with dedicated RX and TX interrupts (all except MT7621 and
MT7628) platform_get_irq() is called for the first IRQ (eth->irq[0])
but it is never used.
Skip the first IRQ and reduce the IRQ-count to 2.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250619132125.78368-4-linux@fw-web.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>