shadow: upgrade from 4.15.0 to 4.15.1

0001-lib-copydir-copy_entry-use-temporary-stat-buffer.patch is dropped
as it has been merged and is in this new release.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>