Since diagonal key support was added in kernel 4.7 KEY_LEFT_UP
and KEY_RIGHT_UP are valid input symbols.
This means we can no longer use _UP as a suffix for transporting
release events from lircd to lircd-uinput, lircd-uinput now
interprets KEY_LEFT_UP/KEY_RIGHT_UP as a diagnoal key down event
instead of left/right key release.