Update version for v2.11.0-rc0 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index e8bd316..098bbf1 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.10.50
+2.10.90