ARM: dts: OMAP5: uevm: Fix "debounce-interval" property misspelling

"debounce_interval" was never supported.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Benoît Cousson <bcousson@baylibre.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>