Update version for v2.5.0-rc2 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 1e245dc..0e95c7d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.4.91
+2.4.92