staging: gasket: fix mmap of coherent buffer when IOMMU translation on

Coherent buffer mmap code assumes DMA addresses are physical addresses,
which is patently wrong when a downstream IOMMU allocates and
translates IOVAs for DMA mappings.  Use dma_mmap_coherent().

Bug: 140076240
Bug: 111709861
Change-Id: Ieaa052378844aaf126ea3bc9dba544e7edb37bc7
Signed-off-by: Todd Poynor <toddpoynor@google.com>
1 file changed