myri10ge: move request_irq to myri10ge_open

Request IRQ in myri10ge_open() and free in close() instead of probe()
and remove() to eliminate potential race between the watchdog and the
interrupt handler. Additionaly, the interrupt handler won't get called
on shared irq anymore when the interface is down.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>