Since people seem to make a point in breaking the userspace visible
counter, we have no choice but to trap the access. Add the required
handler.

Bug: 68266545
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
(cherry picked from commit 6126ce05)

Change-Id: I0705f47c85a78040df38df18f51a4a22500b904d