Revert "drm: Add solid fill pixel source"

This reverts commit 4b641670.

Although the Solid Fill planes patchset got all reviews and
acknowledgements, it doesn't fulfill requirements for the new uABI. It
has neither corresponding open-source userspace implementation nor the
IGT tests coverage. Reverting this patchset until userspace obligations
are fulfilled.

Acked-by: Simon Ser <contact@emersion.fr>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231204131455.19023-6-dmitry.baryshkov@linaro.org