kernel/msm: hdcp: Add API to enforce/revoke forced encryption

The new API will improve modularization, segregate enablement
and enforcement of encryption for DisplayPort.

CRs-Fixed: 2231930
Change-Id: If58c0663ce1894be8ac5e12d6d90cf590fc920b1
Signed-off-by: Mohamed Sunfeer <msunfeer@codeaurora.org>