The ROOTFS_SIZE calculation was not correctly taking into account
the IMAGE_ROOTFS_EXTRA_SPACE variable, it would only be applied if
the size as determined by the ((du * overhead) + extra space) was
greater than the IMAGE_ROOTFS_SIZE, so if the du * overhead was smaller
Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>