hkbd(4): Fix key repeats on multireport keyboards

Currently hkbd counts all key states to be "Up" at the start of
interrupt callback. That results in generation of "Key Up" event for
each key that has been downed before but is not listed in current
report while is still downed.

Fix that with clearing of temporary key data storage bits only for
keys contained in processed report.

Reported by: Greg V
Obtained from: sysutils/iichid
MFC after: 2 weeks