BugLink: https://bugs.launchpad.net/bugs/1820872

Add 'nosmt' which was omitted in the original backport.

Fixes: df8ddbcb ("cpu/hotplug: Provide knobs to control SMT")
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>