drm/i915/hdcp: update current transcoder into intel_hdcp

On gen12+ platforms, HDCP HW is associated to the transcoder.
Hence on every modeset update associated transcoder into the
intel_hdcp of the port.

v2:
  s/trans/cpu_transcoder [Jani]
v3:
  comment is added for fw_ddi init for gen12+ [Shashank]
  only hdcp capable transcoder is translated into fw_tc [Shashank]
v4:
  fw_tc initialization is kept for modeset. [Tomas]
  few extra doc is added at port_data init [Tomas]
v5:
  Few comments are improvised [Tomas]

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190828164216.405-6-ramalingam.c@intel.com