The platform_get_irq_byname() returns non-zero IRQ number
or negative error number. "if (irq)" always true, chang it
to "if (irq > 0)"
Signed-off-by: NLi Qiong <liqiong@nfschina.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>