xen/passthrough: Render domains with %pd in the 'Q' debug handler

xen/passthrough: Render domains with %pd in the 'Q' debug handler

IOMMUs are owned by DOM_XEN, and with XSA-302, DOM_IO is used for
quarantined devices.  Use %pd in the printk to render the system
domains more intelligently.

Before:
  (XEN) 0000:00:01.0 - dom 0   - node 0   - MSIs < >
  (XEN) 0000:00:00.0 - dom 0   - node 0   - MSIs < >
  (XEN) 0000:80:00.2 - dom 32754 - node 1   - MSIs < >
  (XEN) 0000:a0:00.2 - dom 32754 - node 1   - MSIs < >
  (XEN) 0000:c0:00.2 - dom 32754 - node 1   - MSIs < >
  (XEN) 0000:e0:00.2 - dom 32754 - node 1   - MSIs < >
  (XEN) 0000:00:00.2 - dom 32754 - node 0   - MSIs < >
  (XEN) 0000:20:00.2 - dom 32754 - node 0   - MSIs < >
  (XEN) 0000:40:00.2 - dom 32754 - node 0   - MSIs < >
  (XEN) 0000:60:00.2 - dom 32754 - node 0   - MSIs < >

After:
  (XEN) 0000:00:01.0 - d0 - node 0   - MSIs < >
  (XEN) 0000:00:00.0 - d0 - node 0   - MSIs < >
  (XEN) 0000:80:00.2 - d[XEN] - node 1   - MSIs < >
  (XEN) 0000:a0:00.2 - d[XEN] - node 1   - MSIs < >
  (XEN) 0000:c0:00.2 - d[XEN] - node 1   - MSIs < >
  (XEN) 0000:e0:00.2 - d[XEN] - node 1   - MSIs < >
  (XEN) 0000:00:00.2 - d[XEN] - node 0   - MSIs < >
  (XEN) 0000:20:00.2 - d[XEN] - node 0   - MSIs < >
  (XEN) 0000:40:00.2 - d[XEN] - node 0   - MSIs < >
  (XEN) 0000:60:00.2 - d[XEN] - node 0   - MSIs < >

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>