net: lan966x: Do not check 0 for platform_get_irq_byname()

Since platform_get_irq_byname() never returned zero, so it need not to
check whether it returned zero, it returned -EINVAL or -ENXIO when
failed, so we replace the return error code with the result it returned.

Signed-off-by: Zhu Wang <wangzhu9@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>