jme: netpoll support

This patch adds the netpoll function to support netconsole. Tested and works
fine on my "JMC250 PCI Express Gigabit Ethernet Controller" (PCI ID 0250).

Signed-off-by: Peter Wu <lekensteyn@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>