drm/exynos: ipp: Remove Exynos DRM IPP subsystem

drm/exynos: ipp: Remove Exynos DRM IPP subsystem

Exynos DRM IPP subsystem is in fact non-functional and frankly speaking
dead-code. This patch clearly marks that Exynos DRM IPP subsystem is
broken and never really functional. It will be replaced by a completely
rewritten API.

Exynos DRM IPP user-space API can be obsoleted for the following
reasons:

1. Exynos DRM IPP user-space API can be optional in Exynos DRM, so
userspace should not rely that it is always available and should have
a software fallback in case it is not there.

2. The only mode which was initially semi-working was memory-to-memory
image processing. The remaining modes (LCD-"writeback" and "output")
were never operational due to missing code (both in mainline and even
vendor kernels).

3. Exynos DRM IPP mainline user-space API compatibility for
memory-to-memory got broken very early by commit 083500baefd5 ("drm:
remove DRM_FORMAT_NV12MT", which removed the support for tiled formats,
the main feature which made this API somehow useful on Exynos platforms
(video codec that time produced only tiled frames, to implement xvideo
or any other video overlay, one has to de-tile them for proper
display).

4. Broken drivers. Especially once support for IOMMU has been added,
it revealed that drivers don't configure DMA operations properly and in
many cases operate outside the provided buffers trashing memory around.

5. Need for external patches. Although IPP user-space API has been used
in some vendor kernels, but in such cases there were additional patches
applied (like reverting mentioned 083500baefd5 patch) what means that
those userspace apps which might use it, still won't work with the
mainline kernel version.

We don't have time machines, so we cannot change it, but Exynos DRM IPP
extension should never have been merged to mainline in that form.

Exynos IPP subsystem and user-space API will be rewritten, so remove
current IPP core code and mark existing drivers as BROKEN.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>