freedreno/registers/mdp5: fix validation error

Empty enums are not allowed.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6107>
diff --git a/src/freedreno/registers/mdp/mdp5.xml b/src/freedreno/registers/mdp/mdp5.xml
index a5ae1e3..117b43d 100644
--- a/src/freedreno/registers/mdp/mdp5.xml
+++ b/src/freedreno/registers/mdp/mdp5.xml
@@ -63,6 +63,8 @@
 	</enum>
 
 	<enum name="mdp5_format">
+		<!-- TODO -->
+		<value name="DUMMY" value="0"/>
 	</enum>
 
 	<enum name="mdp5_ctl_mode">