xl: xl.cfg: fix typo in opengl section

Add missing i to qemu-xen-traditonal

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

docs/man/xl.cfg.pod.5

@@ -278,7 +278,7 @@ Simple DirectMedia Layer). The default is to not enable this mode
 =item C<opengl=BOOLEAN>
 
 Enable OpenGL acceleration of the SDL display. Only effects machines
-using C<device_model_version="qemu-xen-traditonal"> and only if the
+using C<device_model_version="qemu-xen-traditional"> and only if the
 device-model was compiled with OpenGL support. Disabled by default.
 
 =item C<keymap="LANG">