smsc75xx: don't call usbnet_resume if usbnet_suspend fails

If usbnet_suspend returns an error we don't want to call
usbnet_resume to clean up, but instead just return the error.

If usbnet_suspend *does* succeed, and we have a problem further
on, the desired behaviour is still to call usbnet_resume
to clean up before returning.

Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>