phy: micrel: Reenable interrupts during resume for ksz9031

Like the ksz8081, the ksz9031 has the behavior where it will clear the
interrupt enable bits when leaving power down. This takes advantage of the
solution provided by f5aba91d.

Signed-off-by: Xander Huff <xander.huff@ni.com>
Signed-off-by: Nathan Sullivan <nathan.sullivan@ni.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>