dt-bindings: atmel-tcb: convert bindings to json-schema

Convert Atmel Timer Counter Blocks bindings to DT schema format using
json-schema.

Also move it out of mfd as it is not and has never been related to mfd.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>