x86/bugs/IBRS: Keep SSBD mitigation in effect if spectre_v2=ibrs is selected

x86/bugs/IBRS: Keep SSBD mitigation in effect if spectre_v2=ibrs is selected

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

If the system admins picks to disable memory disambiguation at bootup
(spec_store_bypass_disable=on) and enable IBRS (spectre_v2=ibrs) we
end up briefly at bootup disabling memory disambiguation and then
IBRS SPEC_CTRL kicks - and memory disambiguation is enabled back again.

The logic is there for the 'auto' case, but we missed it for
the other ones. Lets fix it up.

OraBug: 28071800

Fixes: 89981b51b9240ec16e506304990ce2311e93285b ("x86/speculation: Add prctl for Speculative Store Bypass mitigation")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>