hwmon: (w83795) Unconditionally support manual fan speed control

Manual fan speed control uses a standard interface and has received
sufficient testing and review by now, it can be enabled
unconditionally. This includes attributes pwm[1-8], pwm[1-8]_enable,
pwm[1-8]_mode and pwm[1-8]_freq.

We only let the user switch from automatic mode to manual mode, but
not the other way around, as automatic control settings may not have
been set properly by the BIOS.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>