hw/vfio: Add number of dirty pages to vfio_get_dirty_bitmap tracepoint

hw/vfio: Add number of dirty pages to vfio_get_dirty_bitmap tracepoint

Include the number of dirty pages on the vfio_get_dirty_bitmap tracepoint.
These are fetched from the newly added return value in
cpu_physical_memory_set_dirty_lebitmap().

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Message-Id: <20230530180556.24441-3-joao.m.martins@oracle.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>