x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock()

If CONFIG_PARAVIRT_SPINLOCKS=y, queued_spin_unlock() is implemented
using pv_queued_spin_unlock() which is entirely inline asm based. As
such, we do not receive any KCSAN barrier instrumentation via regular
atomic operations.

Add the missing KCSAN barrier instrumentation for the
CONFIG_PARAVIRT_SPINLOCKS case.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>