Version bump on develop after release.

Change-Id: I807e1c2475ae5e64b337988475e69bf723c01746
diff --git a/ARM.CMSIS.pdsc b/ARM.CMSIS.pdsc
index 0684a32..f95bd99 100644
--- a/ARM.CMSIS.pdsc
+++ b/ARM.CMSIS.pdsc
@@ -8,6 +8,9 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
+    <release version="5.4.1-dev0">
+      Active development ...
+    </release>
     <release version="5.4.0" date="2018-08-01">
       Aligned pack structure with repository.
       The following folders are deprecated: