hwmon: (f75375s) Fix register write order when setting fans to full speed

By hwmon sysfs interface convention, setting pwm_enable to zero sets a fan
to full speed.  In the f75375s driver, this need be done by enabling
manual fan control, plus duty mode for the F875387 chip, and then setting
the maximum duty cycle.  Fix a bug where the two necessary register writes
were swapped, effectively discarding the setting to full-speed.

Signed-off-by: Nikolaus Schulz <mail@microschulz.de>
Cc: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>