msm: iommu: Fix SMR NSCFG configuration

When setting the NSCFG field, the S2CR register being
written needs to be indexed by the stream matching group,
not by the value of the SID being configured. Additionally,
there is no need to set CBACR for every SMR that is
programmed.

Change-Id: Ib79771a3bd87e4bd3b353bd5c6de9247138ca43e
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>