usbnet: fix deadlock in resume

A usbnet device can share a multifunction device
with a storage device. If the storage device is autoresumed
the usbnet devices also needs to be autoresumed. Allocating
memory with GFP_KERNEL can deadlock in this case.

This should go back into all kernels that have
commit 65841fd5
That is 3.5

Signed-off-by: Oliver Neukum <oneukum@suse.de>
CC: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>