skge: use unique IRQ name

Most network drivers request their IRQ when the interface is activated.
skge does it in ->probe() instead, because it can work with two-port
cards where the two net_devices use the same IRQ. This works fine most
of the time, except in some situations when the interface gets renamed.
Consider this example:

1. modprobe skge
   The card is detected as eth0 and requests IRQ 17. Directory
   /proc/irq/17/eth0 is created.
2. There is an udev rule which says this interface should be called
   eth1, so udev renames eth0 -> eth1.
3. modprobe 8139too
   The Realtek card is detected as eth0. It will be using IRQ 17 too.
4. ip link set eth0 up
   Now 8139too requests IRQ 17.

The result is:
WARNING: at fs/proc/generic.c:590 proc_register ...
proc_dir_entry '17/eth0' already registered
...
And "ls /proc/irq/17" shows two subdirectories, both called eth0.

Fix it by using a unique name for skge's IRQ, based on the PCI address.
The naming from the example then looks like this:
$ grep skge /proc/interrupts
 17:        169   IO-APIC-fasteoi   skge@pci:0000:00:0a.0, eth0

irqbalance daemon will have to be taught to recognize "skge@" as an
Ethernet interrupt. This will be a one-liner addition in classify.c. I
will send a patch to irqbalance if this change is accepted.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>