Privious check-in "yocto_kernel: check current items before add a
new one" had been merged before I apply the feedback from Zanussi, Tom.
Now fix it as a new patch.
This fix modify the output message when customer adding duplicate
items.
[YOCTO #4558]
(From meta-yocto rev: 530c6efa85b1798d30db4c6c83a748b100b8c1c3)
Signed-off-by: Ning Zhang <ning.zhang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>