x86: assorted array_index_nospec() insertions

x86: assorted array_index_nospec() insertions

Don't chance having Spectre v1 (including BCBS) gadgets. In some of the
cases the insertions are more of precautionary nature rather than there
provably being a gadget, but I think we should err on the safe (secure)
side here.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>