coresight: Add support to disable link in later phase

Some coresight source keeps trace events in buffer after source
is disabled. These trace events need to be flushed out when sink
is disabled otherwise they will be flushed out in next trace
session. In order to flush the data out, all links need to be
kept enabled until sink is disabled. Put the disablement of
link after sink is disabled.

Change-Id: Ie19d5acf622e9ce256f121c05a0d70a8d303d76a
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>