target/s390x/cpu_models: Drop local @err in get_max_cpu_model()

Use @errp to fetch error information directly and drop the local
variable @err.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20240425031232.1586401-6-zhao1.liu@intel.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
1 file changed