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

"make dtbs_check":

    arch/arm/boot/dts/am3874-iceboard.dtb: pca9548@70: $nodename:0: 'pca9548@70' does not match '^(i2c-?)?mux'
	    From schema: Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
    arch/arm/boot/dts/am3874-iceboard.dtb: pca9548@70: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'i2c@0', 'i2c@1', 'i2c@2', 'i2c@3', 'i2c@4', 'i2c@5', 'i2c@6', 'i2c@7' were unexpected)
	    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>
Message-Id: <bc964109db8a5f29124580165e925bd3bfe36661.1669999298.git.geert+renesas@glider.be>
Signed-off-by: Tony Lindgren <tony@atomide.com>