Coresight: change attribute names for sources and sinks

Use 'enable' instead of 'enable_source' and 'curr_sink' instead of
'enable_sink attributes to align it with MSM implementation.

This change ensures same device node interface for host tools
between MSM and upstream Coresight driver implementation.

Change-Id: I5267d2ad92e76607e0ac1bd0e9ef63c0a89cfe7f
Signed-off-by: Shashank Mittal <mittals@codeaurora.org>