initramfs-framework/setup-live: also boot live image if root=/dev/ram0

initramfs-framework/setup-live: also boot live image if root=/dev/ram0

Our grub and syslinux bootloaders both define root=/dev/ram0 for live
images by default. Kernel docs show that root=/dev/ram0 is just a
sentinel value for the kernel to mount the initrd as root, which then
mounts and switches to the real root. This is exactly what our scripts
do, so just check for root=/dev/ram0 as well.

See: https://www.kernel.org/doc/html/v4.11/admin-guide/initrd.html#operation

This fixes the issue where the new initramfs-framework scripts would not
boot live images that use grub or syslinux bootloaders.

Signed-off-by: California Sullivan <california.l.sullivan@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>