atkbd(4): Fix "hancha" and "han/yong" korean keys handling.

The Korean keyboard has two keys, the Korean/Chinese and the
Korean/English toggles, that generate scancodes 0xF1 and 0xF2
(respectively) when pressed, and nothing when released. They do not
repeat.
As Hanyong/Hancha keys are generally greater than 0x80, which is
generally considered a release key, add extra preceding press key event
to generate press/release pair.
Swap Hanyong/Hancha key codes to match reality.

Reported by: Warioburn <warioburn@yahoo.co.jp>
PR: 265260
MFC after: 1 week