target-i386: Update model values on Conroe/Penryn/Nehalem CPU models

The CPUID model values on Conroe, Penryn, and Nehalem are too
conservative and don't reflect the values found on real Conroe, Penryn,
and Nehalem CPUs.

This causes at least one known problems: Windows XP disables sysenter
when (family == 6 && model <= 2), but Skype tries to use the sysenter
instruction anyway because it is reported as available on CPUID, making
it crash.

This patch sets appropriate model values that correspond to real Conroe,
Penryn, and Nehalem CPUs.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
