Input: LEDs - skip unnamed LEDs

Devices may declare more LEDs than what is known to input-leds
(HID does this for some devices). Instead of showing ugly warnings
on connect and, even worse, oopsing on disconnect, let's simply
ignore LEDs that are not known to us.

Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>