ARM: dts: atlas7: Fix "debounce-interval" property misspelling

"debounce_interval" was never supported.

Link: https://lore.kernel.org/r/20191101160356.32034-3-geert+renesas@glider.be


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Barry Song <baohua@kernel.org>
Signed-off-by: Olof Johansson <olof@lixom.net>