commit 1757d05f3112acc5c0cdbcccad3afdee99655bf9 upstream

This patch add a helper to get the value of desired performance
register.
Signed-off-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
[ rjw: More white space ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NZou Cao <zoucao@linux.alibaba.com>
Reviewed-by: NBaoyou Xie <xie.baoyou@linux.alibaba.com>