platform/x86: fujitsu-laptop: simplify logolamp_get()

Now that call_fext_func() is invoked by logolamp_set() for both
LOGOLAMP_POWERON and LOGOLAMP_ALWAYS for every brightness value,
logolamp_get() can be simplified to decrease indentation and number of
local variables.

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>