dt-bindings: spmi: Correct 'reg' schema

'reg' is defined to be N address entries of M cells each. For SPMI, N is 1
and M is 1 or 2. The schema fails to define the number of entries as it
only specifies the inner cell(s). To fix, add an outer items list with 1
entry.

Cc: Stephen Boyd <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/spmi/spmi.yaml

···
 
     properties:
       reg:
-        minItems: 1
-        maxItems: 2
         items:
-          - minimum: 0
-            maximum: 0xf
-          - enum: [ 0 ]
-            description: |
-              0 means user ID address. 1 is reserved for group ID address.
+          - minItems: 1
+            items:
+              - minimum: 0
+                maximum: 0xf
+              - enum: [ 0 ]
+                description:
+                  0 means user ID address. 1 is reserved for group ID
+                  address.
 
     required:
       - reg