mdss: hdmi: sysfs node for hdcp status

The change provides the sysfs node to query hdcp authentication
status. "status" node under hdcp folder will be:
not available: if target doesn't support HDCP
0: inactive
1: authenticating
2: authentication pass
3: authentication fail

Change-Id: I685a25566cfee9cbc89b14263e30a4af3a410f7d
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>