drivers: sensor: sensirion: shtcx: remove chip property

Removes the dts "chip" property, the compatible should be used instead.

Any existing dts should be converted from something like:

test_i2c_shtc3: shtc3@70 {
	compatible = "sensirion,shtcx";
	reg = <0x70>;
	chip = "shtc3";
	measure-mode = "normal";
	clock-stretching;
};

to something like:

test_i2c_shtc3: shtc3@70 {
	compatible = "sensirion,shtc3", "sensirion,shtcx";
	reg = <0x70>;
	measure-mode = "normal";
	clock-stretching;
};

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>