dt-bindings: iio: magnetometer: bmc150: Document regulator supplies

BMC150 needs VDD and VDDIO regulators that might need to be explicitly
enabled. Document support for vdd/vddio-supply to implement this.

Reviewed-by: Linus Walleij <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Stephan Gerhold <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/iio/magnetometer/bosch,bmc150_magn.yaml

···
   reg:
     maxItems: 1
 
+  vdd-supply: true
+  vddio-supply: true
+
   interrupts:
     maxItems: 1