Update version for v4.2.0 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 732b8fa..6aba2b2 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.1.95
+4.2.0