x86/microcode: Allow late microcode loading with SMT disabled

x86/microcode: Allow late microcode loading with SMT disabled

The kernel unnecessarily prevents late microcode loading when SMT is
disabled.  It should be safe to allow it if all the primary threads are
online.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
(cherry picked from commit 07d981ad4cf1e78361c6db1c28ee5ba105f96cc1)

Orabug: 28488808
CVE: CVE-2018-3620

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>