ARM: hisi: rename smp_prepares_cpus function

As hix5hd2 and hip01 has the same .smp_prepare_cpus
in struct smp_operations, so rename hix5hd2_smp_prepare_cpus
to hisi_common_smp_prepare_cpus.

the hip01 will use hisi_common_smp_prepare_cpus in its
struct smp_operations.

Signed-off-by: Wang Long <long.wanglong@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Olof Johansson <olof@lixom.net>