firmware/qcom_scm: Add scm call to handle smmu errata

firmware/qcom_scm: Add scm call to handle smmu errata

Qcom's smmu-500 needs to toggle wait-for-safe sequence to
handle TLB invalidation sync's.
Few firmwares allow doing that through SCM interface.
Add API to toggle wait for safe from firmware through a
SCM call.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Andy Gross <agross@kernel.org>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Will Deacon <will@kernel.org>