dt-bindings: nvmem: Add YAML schemas for the generic NVMEM bindings

The nvmem providers and consumers have a bunch of generic properties that
are needed in a device tree. Add a YAML schemas for those.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
[Srini: Changed licence to (GPL-2.0 OR BSD-2-Clause)]
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>