Documentation: Update QEMU documentation URLs.

The current QEMU documentation URLs, which point to a presumably
old Git repository, appear to time out.
Update it with a new links under https://www.qemu.org/docs

Acked-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Simon Horman <horms@ovn.org>

Documentation/topics/dpdk/vhost-user.rst

@@ -312,7 +312,7 @@ predictable migration time. Mostly used as a second phase after the normal
 
 More information can be found in QEMU `docs`_.
 
-.. _`docs`: https://git.qemu.org/?p=qemu.git;a=blob;f=docs/devel/migration.rst
+.. _`docs`: https://www.qemu.org/docs/master/devel/migration/postcopy.html
 
 Post-copy support may be enabled via a global config value
 ``vhost-postcopy-support``. Setting this to ``true`` enables Post-copy support
@@ -485,7 +485,7 @@ Sample XML
       </devices>
     </domain>
 
-.. _QEMU documentation: http://git.qemu-project.org/?p=qemu.git;a=blob;f=docs/specs/vhost-user.txt;h=7890d7169;hb=HEAD
+.. _QEMU documentation: https://www.qemu.org/docs/master/interop/vhost-user.html
 
 Jumbo Frames
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