qemu: monitor: Allow using 'qdev' instead of 'device' for getting disk throttling

qemu: monitor: Allow using 'qdev' instead of 'device' for getting disk throttling

The 'device' field reported by 'query-block' is empty when -blockdev is
used. Add an argument which will allow matching disk by using the qdev
id so we can use this code with -blockdev.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>