platform/x86: fujitsu-laptop: rework logolamp_set() to properly handle errors

Potential errors returned by some call_fext_func() calls inside
logolamp_set() are currently ignored.  Rework logolamp_set() to properly
handle them.  This causes one more call_fext_func() call to be made in
the LED_OFF case, though one could argue that this is logically the
right thing to do (even though the extra call is not needed to shut the
LED off).

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Acked-by: Jonathan Woithe <jwoithe@just42.net>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>