fixed_phy: pass 'irq' to fixed_phy_add()

I've noticed  that fixed_phy_register() ignores its 'irq' parameter instead of
passing it to fixed_phy_add(). Luckily, fixed_phy_register()  seems to  always
be  called with PHY_POLL  for 'irq'... :-)

Fixes: a7595121

 ("net: phy: extend fixed driver with fixed_phy_register()")
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>