[PATCH] Spidernet stop queue when queue is full.

This patch adds a call to netif_stop_queue() when there is
no more room for more packets on the transmit queue.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>