hwmon: (nct6775-core) Fix out of bounds access for NCT679{8,9}

pwm_num is set to 7 for these chips, but NCT6776_REG_PWM_MODE and
NCT6776_PWM_MODE_MASK only contain 6 values.

Fix this by adding another 0 to the end of each array.

Signed-off-by: Tasos Sahanidis <tasos@tasossah.com>
Link: https://lore.kernel.org/r/20250312030832.106475-1-tasos@tasossah.com


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