ipw2x00: cleanup dead code

Fix smatch warning:

drivers/net/wireless/intel/ipw2x00/ipw2100.c:5606
 shim__set_security() warn: always true condition '(sec->active_key <= 3) => (0-3 <= 3)'
drivers/net/wireless/intel/ipw2x00/ipw2200.c:10725
 shim__set_security() warn: always true condition '(sec->active_key <= 3) => (0-3 <= 3)'

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>