Qualcomm MSS QDSP6v5 Peripheral Image Loader

pil-qdsp6v5-mss is a peripheral image loader (PIL) driver. It is used for
loading QDSP6v5 (Hexagon) firmware images for modem subsystems into memory and
preparing the subsystem's processor to execute code. It's also responsible for
shutting down the processor when it's not needed.

Required properties:
- compatible:	      Must be "qcom,pil-q6v5-mss"
- reg:		      Pairs of physical base addresses and region sizes of
		      memory mapped registers.
- reg-names:	      Names of the bases for the above registers. "qdsp6_base",
		      "halt_base", "rmb_base", "restart_reg", and
		      "metadata_base" are expected.
- interrupts:         The modem watchdog interrupt
- vdd_mss-supply:     Reference to the regulator that supplies the processor.
- vdd_cx-supply:      Reference to the regulator that supplies the vdd_cx domain.
- vdd_mx-supply:      Reference to the regulator that supplies the memory rail.
- qcom,firmware-name: Base name of the firmware image. Ex. "mdsp"
- qcom,pil-self-auth: <0> if the hardware does not require self-authenticating
		      images and self-authentication is not desired;
		      <1> if the hardware requires self-authenticating images.
- qcom,is-loadable:   if PIL is required to load the modem image

Optional properties:
- vdd_pll-supply:     Reference to the regulator that supplies the PLL's rail.
- qcom,vdd_pll:       Voltage to be set for the PLL's rail.

Example:
	qcom,mss@fc880000 {
		compatible = "qcom,pil-q6v5-mss";
		reg = <0xfc880000 0x100>,
		      <0xfd485000 0x400>,
		      <0xfc820000 0x020>,
		      <0xfc401680 0x004>,
		      <0x0d1f0000 0x4000>;
		reg-names = "qdsp6_base", "halt_base", "rmb_base",
			    "restart_reg", metadata_base";
		interrupts = <0 24 1>;
		vdd_mss-supply = <&pm8841_s3>;
		vdd_cx-supply = <&pm8841_s2>;
		vdd_mx-supply = <&pm8841_s1>;

		qcom,is-loadable;
		qcom,firmware-name = "mba";
		qcom,pil-self-auth = <1>;
	};