Update version for v2.9.0-rc4 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index efdab93..b7df49f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.8.93
+2.8.94