tg3: Be drop monitor friendly

tg3_tx() does the normal packet TX completion,
tigon3_dma_hwbug_workaround() and tg3_tso_bug() both need to allocate a
new SKB that is suitable to workaround HW bugs, and finally
tg3_free_rings() is doing ring cleanup. Use dev_consume_skb_any() for
these 3 locations to be SKB drop monitor friendly.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>