hwmon: (pmbus/lm25066) Offset coefficient depends on CL

When converting the DIRECT format CURRENT_IN and POWER commands, make
the offset coefficient ("b") predicate on the value of the current limit
setting.

Signed-off-by: Xo Wang <xow@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>