Avoid using memcpy() to copy structs

We can just use a regular assignment instead. This is more
type-safe since there is no need to provide the struct size.

The remaining memcpy() calls perform array copies or copies from
void pointers (which may be unaligned).

render/allocator/drm_dumb.c

@@ -129,7 +129,7 @@ static void drm_dumb_buffer_end_data_ptr_access(struct wlr_buffer *wlr_buffer) {
 static bool buffer_get_dmabuf(struct wlr_buffer *wlr_buffer,
 		struct wlr_dmabuf_attributes *attribs) {
 	struct wlr_drm_dumb_buffer *buf = drm_dumb_buffer_from_buffer(wlr_buffer);
-	memcpy(attribs, &buf->dmabuf, sizeof(buf->dmabuf));
+	*attribs = buf->dmabuf;
 	return true;
 }