qapi/machine: Rename CpuS390* to S390Cpu*, and drop 'prefix'

qapi/machine: Rename CpuS390* to S390Cpu*, and drop 'prefix'

QAPI's 'prefix' feature can make the connection between enumeration
type and its constants less than obvious.  It's best used with
restraint.

CpuS390Entitlement has a 'prefix' to change the generated enumeration
constants' prefix from CPU_S390_ENTITLEMENT to S390_CPU_ENTITLEMENT.
Rename the type to S390CpuEntitlement, so that 'prefix' is not needed.

Likewise change CpuS390Polarization to S390CpuPolarization, and
CpuS390State to S390CpuState.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20240904111836.3273842-10-armbru@redhat.com>