dt-bindings: firmware: scm: Add SM6350 compatible

Add devicetree compatible for SCM on SM6350 SoC.

Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211213082614.22651-3-luca.weiss@fairphone.com