platform/x86: GPD pocket fan: Allow somewhat lower/higher temperature limits

Allow the user to configure the fan to turn on / speed-up at lower
thresholds then before (20 degrees Celcius as minimum instead of 40) and
likewise also allow the user to delay the fan speeding-up till the
temperature hits 90 degrees Celcius (was 70).

Cc: Jason Anderson <jasona.594@gmail.com>
Reported-by: Jason Anderson <jasona.594@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>