Update version for v7.0.0-rc2 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 61d04b7..030e1ce 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-6.2.91
+6.2.92