x86: cpu: microcode: fix late loading SpectreV2 bugs eval

x86: cpu: microcode: fix late loading SpectreV2 bugs eval

On microcode reloading we have to update the status of SpectreV2 mitigations if
they were not present at init time: we run the logic of selecting the default
mitigation in auto mode.

It was not possible to use the same functions as most of the logic is using
boot_command_line which is in init data and dropped after booting. Also we had
to drop some of the __init clauses on some functions we use in order to not
duplicate them.

This patch is not addressing alternative instructions related to SpectreV2. The
only one that we found so far is STUFF_RSB macro, and it will be addressed
later.

Orabug: 29336760

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>