STMPE ADC driver
----------------

Required properties:
 - compatible: "st,stmpe-adc"

Optional properties:
Note that the ADC is shared with the STMPE touchscreen. ADC related settings
have to be done in the mfd.
- st,norequest-mask: bitmask specifying which ADC channels should _not_ be
  requestable due to different usage (e.g. touch)

Node name must be stmpe_adc and should be child node of stmpe node to
which it belongs.

Example:

	stmpe_adc {
		compatible = "st,stmpe-adc";
		st,norequest-mask = <0x0F>; /* dont use ADC CH3-0 */
	};