BACKPORT: arm64: Add CNTVCT_EL0 trap handler

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.

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: I05700a533ea59e864e7a072605e3000e29526db3
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>