doc: Add link to v1.8 documentation
doc: Add link to v1.8 documentation

Signed-off-by: David B. Kinder <c56c8b29908a5b2af1b63001268d73a0b7f972ba@intel.com>

bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr