arm,scmi.txt used the wrong document identifier. "ARM DUI 0922B" is
the "ARM Compute Subsystem SCP, Message Interface Protocols". What we
need is the ARM DEN 0056A - "ARM System Control and Management
Interface Platform Design Document".

Fixes: fe7be8b2 ("dt-bindings: arm: add support for ARM System Control and Management Interface(SCMI) protocol")
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>