busybox: add /usr/bin/stat applet

busybox: add /usr/bin/stat applet

The busybox defconfig lacks a stat tool, the functionality of which
cannot be reproduced in a way accessible to a shell script running in
a minimal configuration.  Enable, and modify the installation path to
/usr/bin/stat to match the coreutils tool for proper alternatives
handling.

Signed-off-by: Andy Ross <andy.ross@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>