drm/arc: Embedded a drm_simple_display_pipe

This is a prep step to convert arc over to the simple kms helpers, for
now we just use this as an embedding container to drop all the various
allocations. Big change is the removal of the various devm_kzalloc,
which have the wrong lifetimes anyway.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210112084358.2771527-4-daniel.vetter@ffwll.ch