drm/tilcdc: Remove the useless module list support

drm/tilcdc: Remove the useless module list support

The tilcdc driver previously supported a sub-module system where
external display drivers (panels, encoders) could register themselves
through tilcdc_module_init() and be automatically initialized through
a module list. This infrastructure became unused after the component
framework support and panel driver was removed.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Kory Maincent (TI.com) <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20260123-feature_tilcdc-v5-13-5a44d2aa3f6f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>