byte-cntr: Support to enable byte-cntr after etr is enabled

There will be use case that enable byte-cntr after etr is enabled.
Make changes to support it.

Change-Id: Iec32a04e5377b901d7b92aa8b4e2731b75619e81
Signed-off-by: Mao Jinlong <jinlmao@codeaurora.org>