drm/tegra: Include DMA API header where used

Even though the IOVA API never actually needed it, iova.h is still
carrying an include of dma-mapping.h, now solely for the sake of not
breaking tegra-drm. Fix that properly.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -7,6 +7,7 @@
 #include <linux/clk.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
+#include <linux/dma-mapping.h>
 #include <linux/iommu.h>
 #include <linux/interconnect.h>
 #include <linux/module.h>

drivers/gpu/drm/tegra/hub.c

@@ -5,6 +5,7 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dma-mapping.h>
 #include <linux/host1x.h>
 #include <linux/module.h>
 #include <linux/of.h>

drivers/gpu/drm/tegra/nvdec.c

@@ -5,6 +5,7 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dma-mapping.h>
 #include <linux/host1x.h>
 #include <linux/iommu.h>
 #include <linux/module.h>

drivers/gpu/drm/tegra/plane.c

@@ -3,6 +3,7 @@
  * Copyright (C) 2017 NVIDIA CORPORATION.  All rights reserved.
  */
 
+#include <linux/dma-mapping.h>
 #include <linux/iommu.h>
 #include <linux/interconnect.h>