gpu: ion: set dma_address for contiguous heaps in ion_map_dma()

Ion carveout and content protect heap buffers do not
have a struct page associated with them. Thus
sg_phys() will not work reliably on these buffers,
so set dma_address on their scatterlists.

CRs-Fixed: 345257
Change-Id: Ifdad5ce497de170f47b4ee2f7a93563a5cbe1a96
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>