drm/mediatek: Remove all conflicting aperture devices during probe

If a device has a framebuffer available it might be already used as
display by simple-framebuffer or simpledrm when mediatek-drm is probed.
This is actually helpful when porting to a new device as
framebuffers are simple to setup in device trees and fbcon can be
used to monitor the kernel boot process.

When drm-mediatek loads a new fb device is initialized, however
fbcon remains attached to the initial framebuffer which is no longer
connected to the actual display - the early fb is never removed.

We can gracefully transition from framebuffer handling to drm-managed
display by calling aperture_remove_all_conflicting_devices before
registering mediatek-drm. This takes care of unloading other fb
devices/drivers and disconnects fbcon which then automatically
reconnects to mediatekdrmfb as soon as it's available.

The function is invoked just before drm_dev_register() to kick out
the existing framebuffer as late as possible to reduce the time the
screen is unresponsive.

Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20260212192605.263160-1-l.scorcia@gmail.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>