CVE-2018-3639 (x86)

We now have individual feature flags for IBRS and IBPB, so query them when
reloading microcode. Just like we do on boot (in
arch/x86/kernel/cpu/common.c).
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>