tty: Fix LED error return

3.4-rc introduced a regression when setting the LEDS. We do the right thing
but then return an error code.

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=43144
Reported-by: Christian Casteyde
Signed-off-by: Alan Cox <alan@linux/intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>