iommu: msm: Correct bus type being passed to iommu_present

We can now have multiple IOMMU drivers enabled at
same time to support different SMMU hardware IPs.
Since platform bus cannot support more that one
IOMMU ops implementation, we have now added one
more non-secure bus, msm_iommu_non_sec_bus.

Currently we were passing only platform_bus to
iommu_present which was resulting in a BUG when
our SMMU hardware was registered with other bus.
So correct this and now pass generic non_secure
bus type.

Change-Id: I37587fb3e166b2ffd41f09b9d3ce5937d7673456
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>