regulator: dt-bindings: nxp,pca9450: document input supplies

Add missing supply properties for PCA945x input pin groups:
- inl1-supply (for LDOs)
- inb13-supply (for BUCK1/3)
- inb26-supply (for BUCK2/6)
- inb45-supply (for BUCK4/5)

These properties describe external power sources for each input group.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20251027124415.989301-2-o.rempel@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: olerem

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

@@ -41,6 +41,21 @@ properties:
   interrupts:
     maxItems: 1
 
+  inl1-supply:
+    description: Regulator supply for the INL1 pin group, powering LDOx
+
+  inb13-supply:
+    description:
+      Regulator supply for the INB13 pin group, powering BUCK1 and BUCK3.
+
+  inb26-supply:
+    description:
+      Regulator supply for the INB26 pin group, powering BUCK2 and BUCK6.
+
+  inb45-supply:
+    description:
+      Regulator supply for the INB45 pin group, powering BUCK4 and BUCK5.
+
   regulators:
     type: object
     description: |