qemu-doc: mark ppc/prep machine as deprecated

40p machine type should be used instead.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 67b7211..87212b6 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -195,6 +195,12 @@
 These machine types are very old and likely can not be used for live migration
 from old QEMU versions anymore. A newer machine type should be used instead.
 
+@subsection prep (PowerPC) (since 3.1)
+
+This machine type uses an unmaintained firmware, broken in lots of ways,
+and unable to start post-2004 operating systems. 40p machine type should be
+used instead.
+
 @section Device options
 
 @subsection Block device options