msm: ADSPRPC: Allow mapping of IOMMU heap buffers

Map / unmap the IOMMU heap buffers based on SMMU presence so as
to allow for these buffers to be passed to the remote processor
with zero-copy.

Change-Id: I95b3bdd46a8fa6eb3bca660a3900b5d690c12617
Acked-by: Sathish Ambley <sambley@qti.qualcomm.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>