dm9000: acquire irq flags from device tree

The DM9000 supports both active high interrupts and active low interrupts.
This is configured via the attached EEPROM.  In the device-tree case, make sure
that the DM9000 driver passes the correct flags to request_irq.

Signed-off-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>