fjes: Check for error irq

[ Upstream commit db6d6afe382de5a65d6ccf51253ab48b8e8336c3 ]

I find that platform_get_irq() will not always succeed.
It will return error irq in case of the failure.
Therefore, it might be better to check it if order to avoid the use of
error irq.

Fixes: 658d439b ("fjes: Introduce FUJITSU Extended Socket Network Device driver")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>