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.

Change-Id: I425b4dda32f285996178540e551e3168c51da610
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>
Patch-mainline: https://lore.kernel.org/patchwork/patch/1129993/


Signed-off-by: Elliot Berman <eberman@codeaurora.org>