hwmon: (pmbus) Simplify the calculation of variables

Fix the following coccicheck warnings:

./drivers/hwmon/pmbus/pmbus_core.c:1265:24-26: WARNING !A || A && B is
equivalent to !A || B.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Zhong <abaci-bugfix@linux.alibaba.com>
Link: https://lore.kernel.org/r/1611642100-29937-1-git-send-email-abaci-bugfix@linux.alibaba.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>