initrdscripts: fix init-live.sh

initrdscripts: fix init-live.sh

Fix bug: [YOCTO #686]
Because the variable "ROOT_IMAGE" in init-live.sh is not correct, it fails to
run when using liveCD. Modify value of "ROOT_IMAGE" to "isolinux/rootfs.img".
If we want to use liveCD, we also need to add some kernel options related to
CDROM support when compling kernel.

(From OE-Core rev: f9b6f41c9249cc90f7621d446eafae5e5508dd6e)

Signed-off-by: Jingdong Lu <jingdong.lu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>