platform/x86: fujitsu-laptop: do not log LED registration failures

If acpi_fujitsu_laptop_leds_register() returns an error, the latter will
become the return value of acpi_fujitsu_laptop_add(), which in turn will
be reported by driver core.  Simplify code by replacing pr_err() calls
with return statements.  Return 0 instead of result when no errors occur
in order to make the code easier to read.

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