drm/msm/hdcp: fix start sequences and feature support checks

Align the start sequences for HDCP 1.x and 2.x for DisplayPort,
and fix the feature support checks by adding key verification.

CRs-Fixed: 2306118
Change-Id: I92fad16d5f8435d217456b1bb9420e0f09535ef0
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>