Update version for v4.2.0-rc0 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 5f79df7..b9d9a64 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.1.50
+4.1.90