ARM: dts: at91: sama7g5ek: fix debounce delay property for shdwc

There is no atmel,shdwc-debouncer property for SHDWC. The right DT property
is debounce-delay-us. Use it.

Fixes: 16b161bc ("ARM: dts: at91: sama7g5: add shdwc node")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20230523052750.184223-1-claudiu.beznea@microchip.com