Introduce compatible "linaro,scmi-optee" for SCMI transport channel
based on an OP-TEE service invocation. The compatible mandates a
channel ID defined with property "linaro,optee-channel-id".

Link: https://lore.kernel.org/r/20211028140009.23331-1-etienne.carriere@linaro.org
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>