dt-bindings: spmi: remove the constraint of reg property

'reg' is controller specific so we shouldn't even be specifying it here.
Just remove it.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: James Lo <[e-mail]>
Signed-off-by: Hsin-Hsiung Wang <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/spmi/spmi.yaml

···
   $nodename:
     pattern: "^spmi@.*"
 
-  reg:
-    maxItems: 1
-
   "#address-cells":
     const: 2