cpu: Add Haswell-IBRS CPU model

cpu: Add Haswell-IBRS CPU model

This is a variant of Haswell with indirect branch prediction protection.
The only difference between Haswell and Haswell-IBRS is the added
"spec-ctrl" feature.

The Haswell-IBRS model in QEMU is a bit different since Haswell got
several additional features since we added it in cpu_map.xml:
    arat, abm, f16c, rdrand, vme, xsaveopt

Adding them only to the -IBRS variant would confuse our CPU detection
code.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>