target-i386: Disable HLE and RTM on Haswell & Broadwell

All Haswell CPUs and some Broadwell CPUs were updated by Intel to have
the HLE and RTM features disabled. This will prevent
"-cpu Haswell,enforce" and "-cpu Broadwell,enforce" from running out of
the box on those CPUs.

Disable those features by default on Broadwell and Haswell CPU models,
starting on pc-*-2.3. Users who want to use those features can enable
them explicitly on the command-line.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>