soc: qcom: add scm calls for ion and iommu

Add support for required SCM calls that gets called from ion and iommu
drivers to get services from TZ. Also make is_scm_armv8() global so
that it will be called by required modules.

Change-Id: I476f7873118fa56590385f6cde198210ab31ed6c
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>