dt-bindings: remoteproc: st,stm32-rproc: Rework reset declarations

With the introduction of the SCMI (System Control and Management
Interface), it is now possible to use the SCMI to handle the
hold boot instead of a dedicated SMC call.

As consequence two configurations are possible:
- without SCMI server on OP-TEE:
  use the Linux rcc reset service and use syscon for the MCU hold boot
- With SCMI server on OP-TEE:
  use the SCMI reset service for both the MCU reset and the MCU hold boot.

This patch:
- make optional and deprecated the use of the property st,syscfg-tz
  which was used to check if the trusted Zone was enable to use scm call,
  to manage the hold boot. The reset controller phandle is used instead
  to select the configurations.
- make st,syscfg-holdboot optional
- adds properties check on resets definitions.
- adds an example of the SCMI reset service usage.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230512093926.661509-2-arnaud.pouliquen@foss.st.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>