drm: bridge: cdns-mhdp8546: Enable HDCP

This patch enable HDCP in MHDP driver.

Signed-off-by: Parshuram Thombare <pthombar@cadence.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1618078542-30679-1-git-send-email-pthombar@cadence.com