pc: clean up COMPAT macro chaining

Since commit
 bacc344c ("machine: add properties to compat_props incrementaly")
there is no need to chain per machine type compat macro.

Clean up places where it was done anyway so it will be
consistent and won't confuse contributors during addtion
of new machine types.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>