msm: scm: Add scm_call_atomic3

Some drivers need to pass three arguments atomically. Add support
for it.

Change-Id: Id0f962400c5c4f721eef44069fc3db1779248ae3
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>