dt-bindings: cpu: Fix JSON schema

dt-bindings: cpu: Fix JSON schema

Commit fd73403a4862 ("dt-bindings: arm: Add SMP enable-method for
Milbeaut") added support for a new cpu enable-method, but did so using
tabulations to ident. This is however invalid in the syntax, and resulted
in a failure when trying to use that schemas for validation.

Use spaces instead of tabs to indent to fix this.

Fixes: fd73403a4862 ("dt-bindings: arm: Add SMP enable-method for Milbeaut")
Signed-off-by: Maxime Ripard <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
Acked-by: Sugaya Taichi <[email protected]>
Signed-off-by: Olof Johansson <[email protected]>