dt: bindings: add dt entry flag to skip SCM call for msa region

Add boolean context flag to disable SCM call for statically
mapped msa region.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>