powerpc/pseries: Set or clear security feature flags

powerpc/pseries: Set or clear security feature flags

Now that we have feature flags for security related things, set or
clear them based on what we receive from the hypercall.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
[backport: hunk 2: make pseries_setup_rfi_flush() static]
Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
CVE-2018-3639 (powerpc)

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>