sensor: pms7003: Convert to DTS

Convert pms7003 sensor driver to utilize device tree.

DTS would look something like the following for the pms7003:

uart {
	pms7003: pms7003 {
		 status = "okay";
		 compatible = "plantower,pms7003";
		 label = "pms7003";
	};
};

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>