hwmon: (pmbus/lm25066) Mark lm25066_coeff array const

lm25066_coeff is read-only. Mark it as such.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Link: https://lore.kernel.org/r/20210928092242.30036-6-zev@bewilderbeest.net


[groeck: Added description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>