net: forcedeth: Fix wake-on-lan regression

Commit f55c21fd

 ("forcedeth: call
restore mac addr in nv_shutdown path"), which was introduced to fix
the regression tracked at
http://bugzilla.kernel.org/show_bug.cgi?id=11358 causes the
wake-on-lan mac to be reversed in the shutdown path.  Apparently the
forcedeth situation is rather messy in that the mac we need to
writeback for a subsequent modprobe to work is exactly the reverse of
what is needed for proper wake-on-lan.

The following patch explains the situation in the comments and
makes the call to nv_restore_mac_addr() conditional (only called if
we are not really going for poweroff).

Tobias Diedrich wrote:
> Hmm, I had not tried WOL for some time.
> With 2.6.29-rc3 is see the following behaviour:
> 
> State            WOL Behaviour
> ------------------------------
> shutdown         reversed MAC
> disk/shutdown    reversed MAC
> disk/platform    OK
> 
> Apparently nv_restore_mac_addr() restores the MAC in the wrong order
> for WOL (at least for my PCI_DEVICE_ID_NVIDIA_NVENET_15).  platform
> works, because the MAC is not touched in the nv_suspend() path.
> 
> A possible fix might be to only call nv_restore_mac_addr() if
> system_state != SYSTEM_POWER_OFF.

With the following patch:
shutdown         OK
disk/shutdown    OK
disk/platform    OK
kexec            OK

Signed-off-by: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Tested-by: Philipp Matthias Hahn <pmhahn@titan.lahn.de>
Signed-off-by: David S. Miller <davem@davemloft.net>