* AsahiKASEI AK8975 magnetometer sensor

Required properties:

  - compatible : should be "asahi-kasei,ak8975"
  - reg : the I2C address of the magnetometer

Optional properties:

  - gpios : should be device tree identifier of the magnetometer DRDY pin
  - vdd-supply: an optional regulator that needs to be on to provide VDD
  - mount-matrix: an optional 3x3 mounting rotation matrix

Example:

ak8975@c {
        compatible = "asahi-kasei,ak8975";
        reg = <0x0c>;
        gpios = <&gpj0 7 0>;
        vdd-supply = <&ldo_3v3_gnss>;
        mount-matrix = "-0.984807753012208",  /* x0 */
                       "0",                   /* y0 */
                       "-0.173648177666930",  /* z0 */
                       "0",                   /* x1 */
                       "-1",                  /* y1 */
                       "0",                   /* z1 */
                       "-0.173648177666930",  /* x2 */
                       "0",                   /* y2 */
                       "0.984807753012208";   /* z2 */
};