parisc: don't set ARCH_NO_COHERENT_DMA_MMAP

parisc is the only architecture that sets ARCH_NO_COHERENT_DMA_MMAP
when an MMU is enabled.  AFAIK this is because parisc CPUs use VIVT
caches, which means exporting normally cachable memory to userspace is
relatively dangrous due to cache aliasing.

But normally cachable memory is only allocated by dma_alloc_coherent
on parisc when using the sba_iommu or ccio_iommu drivers, so just
remove the .mmap implementation for them so that we don't have to set
ARCH_NO_COHERENT_DMA_MMAP, which I plan to get rid of.
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/parisc/Kconfig

@@ -52,7 +52,6 @@ config PARISC
 	select GENERIC_SCHED_CLOCK
 	select HAVE_UNSTABLE_SCHED_CLOCK if SMP
 	select GENERIC_CLOCKEVENTS
-	select ARCH_NO_COHERENT_DMA_MMAP
 	select CPU_NO_EFFICIENT_FFS
 	select NEED_DMA_MAP_STATE
 	select NEED_SG_DMA_LENGTH

drivers/parisc/ccio-dma.c

@@ -1024,7 +1024,6 @@ static const struct dma_map_ops ccio_ops = {
 	.unmap_page =		ccio_unmap_page,
 	.map_sg = 		ccio_map_sg,
 	.unmap_sg = 		ccio_unmap_sg,
-	.mmap =			dma_common_mmap,
 	.get_sgtable =		dma_common_get_sgtable,
 };
 

drivers/parisc/sba_iommu.c

@@ -1084,7 +1084,6 @@ static const struct dma_map_ops sba_ops = {
 	.unmap_page =		sba_unmap_page,
 	.map_sg =		sba_map_sg,
 	.unmap_sg =		sba_unmap_sg,
-	.mmap =			dma_common_mmap,
 	.get_sgtable =		dma_common_get_sgtable,
 };