dt-bindings: ata: imx: Document 'target-supply'

The 'target-supply' property is used by some i.MX devicetree files.

Document it to fix the following dt-schema warning:

'target-supply' does not match any of the regexes: '^pinctrl-[0-9]+$'

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

Author: fabioestevam

Documentation/devicetree/bindings/ata/imx-sata.yaml

@@ -80,6 +80,9 @@ properties:
   power-domains:
     maxItems: 1
 
+  target-supply:
+    description: Power regulator for the SATA target device.
+
 required:
   - compatible
   - reg