target-arm/kvm64: Add cortex-a53 cpu support

target-arm/kvm64: Add cortex-a53 cpu support

Since commit e353102(target-arm: cpu64: Add support for Cortex-A53) has
added Cortex-A53 cpu support for target-arm, this patch just enables it
for kvm-arm.

Here adding XGENE_POTENZA just makes the enum continuous.

Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Message-id: 1433207452-4512-2-git-send-email-shannon.zhao@linaro.org
[PMM: Don't add the CPU types to cpus_to_try[]; this array only
 lists old CPUs which were supported in pre-PREFERRED_TARGET kernels]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>