ipw2200: fix error return code in ipw_load()

Fix to return -ENOMEM in the ipw_rx_queue_alloc() error handling
case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: John W. Linville <linville@tuxdriver.com>