Since d0ce7e9c the dc232b structure uses the NANOSECONDS_PER_SECOND
definition from "qemu/timer.h".  Include it to allow further includes
cleanup.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180528232719.4721-7-f4bug@amsat.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>