wined3d: Make the volume parameter to volume_load() const.

dlls/wined3d/volume.c

@@ -89,7 +89,7 @@ void volume_set_container(struct wined3d_volume *volume, struct wined3d_texture
 }
 
 /* Context activation is done by the caller. */
-void volume_load(struct wined3d_volume *volume, UINT level, BOOL srgb_mode)
+void volume_load(const struct wined3d_volume *volume, UINT level, BOOL srgb_mode)
 {
     const struct wined3d_gl_info *gl_info = &volume->resource.device->adapter->gl_info;
     const struct wined3d_format *format = volume->resource.format;

dlls/wined3d/wined3d_private.h

@@ -1920,7 +1920,7 @@ static inline struct wined3d_volume *volume_from_resource(struct wined3d_resourc
 }
 
 void volume_add_dirty_box(struct wined3d_volume *volume, const WINED3DBOX *dirty_box) DECLSPEC_HIDDEN;
-void volume_load(struct wined3d_volume *volume, UINT level, BOOL srgb_mode) DECLSPEC_HIDDEN;
+void volume_load(const struct wined3d_volume *volume, UINT level, BOOL srgb_mode) DECLSPEC_HIDDEN;
 void volume_set_container(struct wined3d_volume *volume, struct wined3d_texture *container) DECLSPEC_HIDDEN;
 
 /*****************************************************************************