mac802154: llsec: correctly lookup implicit-indexed keys

Key id comparison for type 1 keys (implicit source, with index) should
return true if mode and id are equal, not false.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>