drm/debugfs: create debugfs late register functions

Although the device-centered debugfs functions can track requests for
the addition of DRM debugfs files at any time and have them added all
at once during drm_dev_register(), they are not able to create debugfs
files for modeset components, as they are registered after the primary
and the render drm_minor are registered.

So, create a drm_debugfs_late_register() function, which is responsible
for dealing with the creation of all the debugfs files for modeset
components at once. Therefore, the functions drm_debugfs_add_file()
and drm_debugfs_add_files() can be used in late_register hooks.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20221219120621.15086-4-mcanal@igalia.com