ARM: dts: at91: align gpio-key node names with dtschema

The node names should be generic and DT schema expects certain pattern
(e.g. with key/button/switch).

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220616005333.18491-38-krzysztof.kozlowski@linaro.org