drm/tegra: Changes for v6.4-rc1

The majority of this is minor cleanups and fixes. Other than those, this
contains Uwe's conversion to the new driver remove callback and Thomas'
fbdev DRM client conversion. The driver can now also be built on other
architectures to easy compile coverage.

Finally, this adds Mikko as a second maintainer for the driver. As a
next step we also want Tegra DRM to move into drm-misc to streamline the
maintenance process.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
From: Thierry Reding <thierry.reding@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406121404.967704-1-thierry.reding@gmail.com