Update the changelog and add the missed bump of the major version

Author: sergey-semenov

sycl/include/CL/sycl/detail/pi.h

@@ -40,10 +40,11 @@
 // changes the API version from 3.5 to 4.6.
 // 5.7 Added new context and ownership arguments to
 //   piextEventCreateWithNativeHandle
-// 6.8 Added new ownership argument to piextProgramCreateWithNativeHandle.
+// 6.8 Added new ownership argument to piextProgramCreateWithNativeHandle. Added
+// piQueueFlush function.
 //
 #include "CL/cl.h"
-#define _PI_H_VERSION_MAJOR 5
+#define _PI_H_VERSION_MAJOR 6
 #define _PI_H_VERSION_MINOR 8
 
 #define _PI_STRING_HELPER(a) #a