Certain modules call copy_user_highpage(), which calls
kmsan_copy_page_meta() under KMSAN, so we need to export the latter.

Link: https://lkml.kernel.org/r/20221024212144.2852069-1-glider@google.com
Link: https://github.com/google/kmsan/issues/89
Fixes: b073d7f8 ("mm: kmsan: maintain KMSAN metadata for page operations")
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>