mm-video: iommu: Fix decoding for devices without IOMMU (e.g some 8660)

MM_HEAP is OR'ed with IOMMU, so it falls back on MM when IOMMU isnt available.

Change-Id: I7fb039b2e0c3f9da2513c121d390cd3cac2b1a84

Conflicts:

	mm-video/vidc/vdec/src/omx_vdec.cpp