regulator: pca9450: Add sd-vsel GPIO

Add the binding documentation for the optional sd-vsel GPIO.
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Link: https://lore.kernel.org/r/20210211105534.38972-2-frieder.schrempf@kontron.deSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/nxp,pca9450-regulator.yaml

@@ -87,6 +87,11 @@ properties:
 
     additionalProperties: false
 
+  sd-vsel-gpios:
+    description: GPIO that is used to switch LDO5 between being configured by
+      LDO5CTRL_L or LDO5CTRL_H register. Use this if the SD_VSEL signal is
+      connected to a host GPIO.
+
 required:
   - compatible
   - reg