mediatek: mt7623: Disable power button reset for U7623-02 board

mediatek: mt7623: Disable power button reset for U7623-02 board

The Unielec U7623 doesn't have a physical power button; I think it's hard
wired so that it turns on automatically when power is applied (unlike the
Banana Pi R2 which is a pain).

So the 'reset on long press of power button' behaviour that we get when
we enable the PMIC keyboard driver is kind of unhelpful. Disable it.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Fixes: 0d3f3323a2 ("mediatek: mt7623: enable more hardware features")