meta-skeleton: rename busybox's bbappend file

As busybox has been upgraded, rename this bbappend file to make it
match the current version of busybox.

(From OE-Core rev: 12e33bd0dc02720122eb8088b08a181b13b6ef0e)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>