clocksource: arm64: register unsecure timer only

clocksource: arm64: register unsecure timer only

Only register non-secure timer for ARM64 kernel. This is to
eliminate the conflict between kernel and secure OS.

Since ARM kernel can run in secure state, leave it unchanged.

bug 1838070

Change-Id: I1aa9fcaab4c818c6badb3a7040723cf743484fb3
Signed-off-by: Bo Yan <byan@nvidia.com>
Reviewed-on: http://git-master/r/1471666
Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
(cherry picked from commit 88cb8e8bb6376d28c17df6e580681707a6b5dfa6)
Reviewed-on: http://git-master/r/1484960