drm/mediatek: Remove unused GEM DMA header include

No longer needed since the removal of dependency on DMA helper.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reported-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20230127165409.3512501-1-robdclark@gmail.com/Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -20,8 +20,8 @@
 #include <drm/drm_fbdev_generic.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem.h>
-#include <drm/drm_gem_dma_helper.h>
 #include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_ioctl.h>
 #include <drm/drm_of.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_vblank.h>