ARM: dts: nuvoton: Fix pca954x i2c-mux node names

"make dtbs_check":

    arch/arm/boot/dts/nuvoton-npcm730-gbs.dtb: i2c-switch@71: $nodename:0: 'i2c-switch@71' does not match '^(i2c-?)?mux'
	    From schema: Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
    ...

Fix this by renaming PCA954x nodes to "i2c-mux", to match the I2C bus
multiplexer/switch DT bindings and the Generic Names Recommendation in
the Devicetree Specification.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>