riscv: dts: 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>
Link: https://lore.kernel.org/r/20220624170811.66395-1-krzysztof.kozlowski@linaro.org
Link: https://lore.kernel.org/all/20220616005224.18391-1-krzysztof.kozlowski@linaro.org/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>