arm64: kernel: implement HW breakpoints CPU PM notifier

When a CPU is shutdown either through CPU idle or suspend to RAM, the
content of HW breakpoint registers must be reset or restored to proper
values when CPU resume from low power states. This patch adds debug register
restore operations to the HW breakpoint control function and implements a
CPU PM notifier that allows to restore the content of HW breakpoint registers
to allow proper suspend/resume operations.

Change-Id: Iac4743acea33d1bcee88b5a2be8c56f035fa3aed
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Git-commit: 60fc6942f6ac124503ed7f8506736a8f56b4ca7e
Git-Repo: git://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git


Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>