rust: add dma coherent allocator abstraction.

Add a simple dma coherent allocator rust abstraction. Based on
Andreas Hindborg's dma abstractions from the rnvme driver, which
was also based on earlier work by Wedson Almeida Filho.

Nacked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@gmail.com>

Author: xyn-ack

rust/bindings/bindings_helper.h

@@ -11,6 +11,7 @@
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
 #include <linux/cred.h>
+#include <linux/dma-mapping.h>
 #include <linux/errname.h>
 #include <linux/ethtool.h>
 #include <linux/file.h>

rust/helpers/dma.c

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-mapping.h>
+
+int rust_helper_dma_set_mask_and_coherent(struct device *dev, u64 mask)
+{
+	return dma_set_mask_and_coherent(dev, mask);
+}
+
+int rust_helper_dma_set_mask(struct device *dev, u64 mask)
+{
+	return dma_set_mask(dev, mask);
+}

rust/helpers/helpers.c

@@ -13,6 +13,7 @@
 #include "build_bug.c"
 #include "cred.c"
 #include "device.c"
+#include "dma.c"
 #include "err.c"
 #include "fs.c"
 #include "io.c"