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

commit f54d4537 upstream.

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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>