net: smsc911x: Move interrupt allocation to open/stop

The /proc/irq/xx information is incorrect for smsc911x because
the request_irq is happening before the register_netdev has the
proper device name. Moving it to the open also fixes the case
of when the device is renamed.

Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>