[PATCH] drm/mediatek: fix implicit function declaration

[Anders Roxell]

When building mtk_drm_drv.o the following build error is seen:

../drivers/gpu/drm/mediatek/mtk_drm_drv.c: In function ‘mtk_drm_kms_init’:
../drivers/gpu/drm/mediatek/mtk_drm_drv.c:291:8: error: implicit declaration of
 function ‘dma_set_max_seg_size’; did you mean ‘drm_rect_adjust_size’? [-Werror=implicit-function-declaration]
  ret = dma_set_max_seg_size(dma_dev, (unsigned int)DMA_BIT_MASK(32));
        ^~~~~~~~~~~~~~~~~~~~
        drm_rect_adjust_size
../drivers/gpu/drm/mediatek/mtk_drm_drv.c:291:52: error: implicit declaration of
 function ‘DMA_BIT_MASK’; did you mean ‘BIT_MASK’? [-Werror=implicit-function-declaration]
  ret = dma_set_max_seg_size(dma_dev, (unsigned int)DMA_BIT_MASK(32));
                                                    ^~~~~~~~~~~~
                                                    BIT_MASK

Rework to add a missing include file 'linux/dma-mapping.h', because that
is the (only) header file containing that declaration.

Fixes: 070955558e82 ("drm/mediatek: set DMA max segment size")
Signed-off-by: Anders Roxell <anders.roxell at linaro.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 54536176bcbb..352b81a7a670 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -10,6 +10,7 @@
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/pm_runtime.h>
+#include <linux/dma-mapping.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
-- 
2.20.1