s390x/cpu: Use timer_free() in the finalize function to avoid memleaks

s390x/cpu: Use timer_free() in the finalize function to avoid memleaks

When running device-introspect-test, a memory leak occurred in the s390_cpu_initfn
function, this patch use timer_free() in the finalize function to fix it.

ASAN shows memory leak stack:

Direct leak of 3552 byte(s) in 74 object(s) allocated from:
    #0 0xfffeb3d4e1f0 in __interceptor_calloc (/lib64/libasan.so.5+0xee1f0)
    #1 0xfffeb36e6800 in g_malloc0 (/lib64/libglib-2.0.so.0+0x56800)
    #2 0xaaad51a8f9c4 in timer_new_full qemu/include/qemu/timer.h:523
    #3 0xaaad51a8f9c4 in timer_new qemu/include/qemu/timer.h:544
    #4 0xaaad51a8f9c4 in timer_new_ns qemu/include/qemu/timer.h:562
    #5 0xaaad51a8f9c4 in s390_cpu_initfn qemu/target/s390x/cpu.c:304
    #6 0xaaad51e00f58 in object_init_with_type qemu/qom/object.c:371
    #7 0xaaad51e0406c in object_initialize_with_type qemu/qom/object.c:515
    #8 0xaaad51e042e0 in object_new_with_type qemu/qom/object.c:729
    #9 0xaaad51e3ff40 in qmp_device_list_properties qemu/qom/qom-qmp-cmds.c:153
    #10 0xaaad51910518 in qdev_device_help qemu/softmmu/qdev-monitor.c:283
    #11 0xaaad51911918 in qmp_device_add qemu/softmmu/qdev-monitor.c:801
    #12 0xaaad51911e48 in hmp_device_add qemu/softmmu/qdev-monitor.c:916

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Gan Qixin <ganqixin@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20201204081209.360524-4-ganqixin@huawei.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>