powerpc/64s: Add new security feature flags for count cache flush

powerpc/64s: Add new security feature flags for count cache flush

Add security feature flags to indicate the need for software to flush
the count cache on context switch, and for the presence of a hardware
assisted count cache flush.

BugLink: https://bugs.launchpad.net/bugs/1822870
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit dc8c6cce9a26a51fc19961accb978217a3ba8c75)
Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>