dt-bindings: arm: scmi: OP-TEE as transport channel for SCMI messages

dt-bindings: arm: scmi: OP-TEE as transport channel for SCMI messages

Introduce compatible "linaro,scmi-optee" for SCMI transport channel
based on an OP-TEE service invocation.

Define "linaro,optee-channel-id" property to identify the OP-TEE SCMI
channel used by the protocol(s). OP-TEE SCMI transport can either use
shared memory or a static shared memory buffer identified by the DT.

These bindings were posted to the Linux kernel DT bindings mailing list
and acked by maintainer [1].

Link: [1] https://lore.kernel.org/linux-arm-kernel/20211029102118.GG6526@e120937-lin/T/
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>