pc: Remove PCLMULQDQ from Westmere on pc-*-1.4 and older

Commit 41cb383f42d0cb51d8e3e25e3ecebc954dd4196f made a guest-visible
change by adding the PCLMULQDQ bit to Westmere without adding
compatibility code to keep the ABI for older machine-types.
Fix it by adding the missing compat code.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
(cherry picked from commit 56383703c060777fd01aaf8d63d5f46d660e9fb9)

Signed-off-by: Andreas Färber <afaerber@suse.de>
Merge tag 'qom-cpu-for-1.5' into stable-1.5-staging

QOM CPUState and X86CPU for stable-1.5

* Fix X86CPU Westmere CPUID for pc-*-1.4 and older

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>