iwlegacy: 4965-mac: Simplify the calculation of variables

Fix the following coccicheck warnings:

./drivers/net/wireless/intel/iwlegacy/4965-mac.c:2596:54-56: WARNING !A
|| A && B is equivalent to !A || B.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1612425608-40450-1-git-send-email-jiapeng.chong@linux.alibaba.com