hwmon: (occ) Fix division by zero issue

hwmon: (occ) Fix division by zero issue

The code in occ_get_powr_avg() invokes div64_u64() without checking the
divisor. In case the divisor is zero, kernel gets an "Division by zero
in kernel" error.

Check the divisor and make it return 0 if the divisor is 0.

Fixes: a36e2e2d9fa8 ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Lei YU <mine260309@gmail.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/1562813088-23708-1-git-send-email-mine260309@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>