* Texas Instruments LMP91000 series of potentiostats

LMP91000: https://www.ti.com/lit/ds/symlink/lmp91000.pdf
LMP91002: https://www.ti.com/lit/ds/symlink/lmp91002.pdf

Required properties:

  - compatible: should be one of the following:
                 "ti,lmp91000"
                 "ti,lmp91002"
  - reg: the I2C address of the device
  - io-channels: the phandle of the iio provider

  - ti,external-tia-resistor: if the property ti,tia-gain-ohm is not defined this
    needs to be set to signal that an external resistor value is being used.

Optional properties:

  - ti,tia-gain-ohm: ohm value of the internal resistor for the transimpedance
    amplifier. Must be 2750, 3500, 7000, 14000, 35000, 120000, or 350000 ohms.

  - ti,rload-ohm: ohm value of the internal resistor load applied to the gas
    sensor. Must be 10, 33, 50, or 100 (default) ohms.

Example:

lmp91000@48 {
	compatible = "ti,lmp91000";
	reg = <0x48>;
	ti,tia-gain-ohm = <7500>;
	ti,rload = <100>;
	io-channels = <&adc>;
};