dt-bindings: Remove more cases of 'allOf' containing a '$ref'

Another round of 'allOf' removals that came in this cycle.

json-schema versions draft7 and earlier have a weird behavior in that
any keywords combined with a '$ref' are ignored (silently). The correct
form was to put a '$ref' under an 'allOf'. This behavior is now changed
in the 2019-09 json-schema spec and '$ref' can be mixed with other
keywords. The json-schema library doesn't yet support this, but the
tooling now does a fixup for this and either way works.

This has been a constant source of review comments, so let's change this
treewide so everyone copies the simpler syntax.

Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/power/supply/sbs,sbs-battery.yaml

@@ -32,16 +32,14 @@ properties:
     description:
       The number of times to retry I2C transactions on I2C IO failure.
     default: 0
-    allOf:
-      - $ref: /schemas/types.yaml#/definitions/uint32
+    $ref: /schemas/types.yaml#/definitions/uint32
 
   sbs,poll-retry-count:
     description:
       The number of times to try looking for new status after an external
       change notification.
     default: 0
-    allOf:
-      - $ref: /schemas/types.yaml#/definitions/uint32
+    $ref: /schemas/types.yaml#/definitions/uint32
 
   sbs,battery-detect-gpios:
     description: