dma-mapping: fix lack of DMA address assignment in generic remap allocator

Commit bfd56cd6 ("dma-mapping: support highmem in the generic remap
allocator") replaced dma_direct_alloc_pages() with __dma_direct_alloc_pages(),
which doesn't set dma_handle and zero allocated memory. Fix it by doing this
directly in the caller function.

Fixes: bfd56cd6 ("dma-mapping: support highmem in the generic remap allocator")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/remap.c

@@ -223,8 +223,14 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
 			arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
 			__builtin_return_address(0));
-	if (!ret)
+	if (!ret) {
 		__dma_direct_free_pages(dev, size, page);
+		return ret;
+	}
+
+	*dma_handle = phys_to_dma(dev, page_to_phys(page));
+	memset(ret, 0, size);
+
 	return ret;
 }