[TG3]: Fix set ring params tx ring size implementation

Fixes the implementation of the ethtool set ring parameters for the
tg3 transmit ring.  The size of tx_pending is taken into account
before doing a netif_wake_queue.  This prevents the interface from
locking up when smaller transmit ring sizes are used.

Signed-off-by: Ranjit Manomohan <ranjitm@google.com>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>