platform/x86: fujitsu-laptop: ignore errors when setting backlight power

Not all Fujitsu laptops support controlling backlight power through the
FUJ02E3 ACPI device.  Remove the debug message informing about a failed
attempt to set backlight power as it may be confusing and the return
value of call_fext_func() is logged anyway.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Jonathan Woithe <jwoithe@just42.net>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>