x86/bugs: Add Cannon lake to RETBleed affected CPU list

Cannon lake is also affected by RETBleed, add it to the list.

Fixes: 6ad0ad2b

 ("x86/bugs: Report Intel retbleed vulnerability")
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>