ANDROID: iommu/arm-smmu-v3-kvm: Don't leak SMMU ref in error path

During attach, if error happens after taking the ref of the SMMUv3, it
must be put back.

Also, add an assertion during free domain that there are no dangling
SMMU refs.

Bug: 357781595
Change-Id: Ic717c5b2a958e58e00e188b68dda754c38014b76
Signed-off-by: Mostafa Saleh <smostafa@google.com>