Fix the following coccicheck warnings:

./net/ipv6/esp6.c:791:16-18: WARNING !A || A && B is equivalent
to !A || B.
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NJiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>