drm/bridge: anx7625: add HDCP support

This patch provides HDCP setting interface for userspace to dynamic
enable/disable HDCP function.

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Xin Ji <xji@analogixsemi.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220106100127.1862702-2-xji@analogixsemi.com