Check for child devices that specify compression, and store the device
specific compression parameters in the display device data struct for
later use. Warn if compression is requested but not available.

Use fairly rigid checks for compression data for starters. These can be
made more dynamic later.

Log about DSC presence in DDI port parse, though this is not universal
across platforms or port types (DSI).

v2: amended debug logging

Bspec: 29885
Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/357d685ba047faf2285138c2f7014a8dee9a12b7.1575974743.git.jani.nikula@intel.com