regulator: dt-bindings: rtq2208: Add specified fixed LDO VOUT property

As the fixed voltage for the LDO is outside the range of the adjustable voltage mode,
the constraints for this scenario are not suitable to represent both modes.
Therefore, A property is added to specify the fixed LDO VOUT.

Examples of fixed LDO VOUT and adjustable LDO VOUT is also added to this version.
Signed-off-by: Alina Yu <alina_yu@richtek.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/c6cb218f6338291525a29ed89a88a42c175127ad.1716870419.git.alina_yu@richtek.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/richtek,rtq2208.yaml

@@ -75,6 +75,12 @@ properties:
         description:
           regulator description for ldo[1-2].
 
+        properties:
+          richtek,fixed-microvolt:
+            description: |
+              This property can be used to set a fixed operating voltage that lies outside
+              the range of the regulator's adjustable mode.
+
 required:
   - compatible
   - reg
@@ -177,6 +183,8 @@ examples:
             };
           };
           ldo1 {
+            /* Fixed LDO VOUT */
+            richtek,fixed-microvolt = <1200000>;
             regulator-min-microvolt = <1200000>;
             regulator-max-microvolt = <1200000>;
             regulator-always-on;
@@ -185,7 +193,8 @@ examples:
             };
           };
           ldo2 {
-            regulator-min-microvolt = <3300000>;
+            /* Adjustable LDO VOUT */
+            regulator-min-microvolt = <1800000>;
             regulator-max-microvolt = <3300000>;
             regulator-always-on;
             regulator-state-mem {