Free RX buffers

Free the RX skb's on shutdown.

Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Use GFP_KERNEL for RX skb allocations

These allocations are done in process / wq context.

Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Merge pull request #32 from pof2/master

Free RX buffers