iommu: msm: Fix SMG resource leak

When detaching a domain from an IOMMU context device, the
associated Stream Matching Group registers need to be
invalidated so that they can be reused by subsequent attach
calls.

Change-Id: I35b1de822238e7214bd329935c76e1eadf25efab
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>