drm/exynos: Use .dumb_map_offset and .dumb_destroy defaults

This driver can use the drm_driver.dumb_destroy and
drm_driver.dumb_map_offset defaults, so no need to set them.
Use drm_gem_dumb_map_offset() in exynos_drm_gem_map_ioctl() and
remove exynos_drm_gem_dumb_map_offset().

Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1502034068-51384-14-git-send-email-noralf@tronnes.org
diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
index c23479b..077de01 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
@@ -286,8 +286,8 @@ int exynos_drm_gem_map_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_exynos_gem_map *args = data;
 
-	return exynos_drm_gem_dumb_map_offset(file_priv, dev, args->handle,
-					      &args->offset);
+	return drm_gem_dumb_map_offset(file_priv, dev, args->handle,
+				       &args->offset);
 }
 
 dma_addr_t *exynos_drm_gem_get_dma_addr(struct drm_device *dev,
@@ -422,32 +422,6 @@ int exynos_drm_gem_dumb_create(struct drm_file *file_priv,
 	return 0;
 }
 
-int exynos_drm_gem_dumb_map_offset(struct drm_file *file_priv,
-				   struct drm_device *dev, uint32_t handle,
-				   uint64_t *offset)
-{
-	struct drm_gem_object *obj;
-	int ret = 0;
-
-	/*
-	 * get offset of memory allocated for drm framebuffer.
-	 * - this callback would be called by user application
-	 *	with DRM_IOCTL_MODE_MAP_DUMB command.
-	 */
-
-	obj = drm_gem_object_lookup(file_priv, handle);
-	if (!obj) {
-		DRM_ERROR("failed to lookup gem object.\n");
-		return -EINVAL;
-	}
-
-	*offset = drm_vma_node_offset_addr(&obj->vma_node);
-	DRM_DEBUG_KMS("offset = 0x%lx\n", (unsigned long)*offset);
-
-	drm_gem_object_unreference_unlocked(obj);
-	return ret;
-}
-
 int exynos_drm_gem_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;