KVM: arm64: Disassociate vcpus from redistributor region on teardown

commit 0d92e4a7 upstream.

When tearing down a redistributor region, make sure we don't have
any dangling pointer to that region stored in a vcpu.

Fixes: e5a35635

 ("kvm: arm64: vgic-v3: Introduce vgic_v3_free_redist_region()")
Reported-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240605175637.1635653-1-maz@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>