dt-bindings: regulator: fixed: add qti-regulator-fixed compatible string

Modify the fixed-regulator binding to include the compatible
string "qti-regulator-fixed".  This is helpful in situations
where proxy consumer voting or debug control features are
needed.

Change-Id: Icf4e6012a0994ff2467ee8a7af036bb97c352fce
Signed-off-by: David Collins <quic_collinsd@quicinc.com>

bindings/regulator/fixed-regulator.yaml

@@ -42,6 +42,7 @@ properties:
       - regulator-fixed
       - regulator-fixed-clock
       - regulator-fixed-domain
+      - qti-regulator-fixed
 
   regulator-name: true