drm/tilcdc: replace late_initcall with module_init

drm/tilcdc: replace late_initcall with module_init

Use module_init instead of late_initcall, as is the norm for modular
drivers.

module_init was used until ec3d6003a3d19c71faad76c3377d55cb703fbdcc
("drm/tilcdc: add encoder slave (v2)") changed it to a late_initcall,
but it does not explain why. Tests show it's working properly with
module_init.

Signed-off-by: Guido Martínez <guido@vanguardiasur.com.ar>
Tested-by: Darren Etheridge <detheridge@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>