Update version for v2.9.0 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index c4ca98f..c8e38b6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.8.95
+2.9.0