phy: IRQ cannot be shared

With the way PHY IRQ handler is implemented (all real handling being pushed to
the workqueue and returning IRQ_HANDLED all the time PHY is active), we cannot
really claim that PHY IRQ can be shared when calling request_irq().

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>