The way these old image files are staged now makes removing them
the default behavior. Thus, this variable has become redundant.
I added a note indicating such.
(From yocto-docs rev: e1db620fdf741b46e54cf1a3715597f81a811818)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>