Bump pack version to 5.6.0-rc1

Change-Id: Id2b0efc7d880696e516f332f9aba1adfd42aeaa4
diff --git a/ARM.CMSIS.pdsc b/ARM.CMSIS.pdsc
index 07bd087..15c1158 100644
--- a/ARM.CMSIS.pdsc
+++ b/ARM.CMSIS.pdsc
@@ -8,7 +8,7 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
-    <release version="5.6.0-rc0">
+    <release version="5.6.0-rc1">
       Active development...
       CMSIS-Core(M): 5.3.0 (see revision history for details)
        - Added provisions for compiler-independent C startup code.