drivers: clocksource: add CPU PM notifier for ARM architected timer

Few control settings done in architected timer as part of initialisation
can be lost when CPU enters deeper power states. They need to be
restored when the CPU is (warm)reset again.

This patch adds CPU PM notifiers to save the counter control register
when entering low power modes and restore it when CPU exits low power.

Change-Id: Ic617dc1a8efd0c5df7a31fb9990b6ead51292df6
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Git-commit 346e7480f1d4740b3d798da60f83f087ea6488b4
Signed-off-by: Trilok Soni <tsoni@codeaurora.org>