input_id: Avoid memory overflow with too long capability masks

input_id: Avoid memory overflow with too long capability masks

Joey Lee <jlee@novell.com> reported a problem on an MSI laptop which reports a
too long capabilities/key:

E: EV==3
E: KEY==180000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

This is longer than KEY_MAX and thus caused a memory overflow. Guard against
this now and just ignore the excess blocks.