hwmon: (corsair-psu) fix plain integer used as NULL pointer

hwmon: (corsair-psu) fix plain integer used as NULL pointer

[ Upstream commit 56f97e0e631a485d1d6fdcc8a3dd357d214645e6 ]

sparse warnings: (new ones prefixed by >>)
>> drivers/hwmon/corsair-psu.c:536:82: sparse: sparse: Using plain
   integer as NULL pointer

Fixes: 877348cfccb9 ("hwmon: add Corsair PSU HID controller driver")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
Link: https://lore.kernel.org/r/YY9hAL8MZEQYLYPf@monster.localdomain
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>