JDK-8057585 UART: The bit flags used for notification status are not set/reset properly

[alexey karaksin]

issue: https://bugs.openjdk.java.net/browse/JDK-8057585
webrev: http://cr.openjdk.java.net/~alkonsta/8057585/

Hi All,

Please review the changes made in order to fix the glitch with bit 
operations for set/reset event notified flag.


Regards,
Alexey