ARM: dts: vf610: Fix pca9548 i2c-mux node names

ARM: dts: vf610: Fix pca9548 i2c-mux node names

"make dtbs_check":

    arch/arm/boot/dts/vf610-zii-dev-rev-b.dtb: tca9548@70: $nodename:0: 'tca9548@70' does not match '^(i2c-?)?mux'
	    From schema: Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
    arch/arm/boot/dts/vf610-zii-dev-rev-b.dtb: tca9548@70: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'i2c@0', 'i2c@1', 'i2c@2', 'i2c@3', 'i2c@4' were unexpected)
	    From schema: /scratch/geert/linux/linux-renesas/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
    ...

Fix this by renaming PCA9548 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>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>