drm:panel: Ported panel-dt driver from i.MX6 kernel

We use a custom Simple Panel driver that allows a more detailed description of
panels in the device tree. This is discouraged by the mainline kernel but has
shown useful for our specific applications.

For a more detailed explanation see the discussion https://patchwork.kernel.org/
project/dri-devel/patch/20190307101030.3822-1-maxime.ripard@bootlin.com/ on
the DRI mailing list and the original commit https://git.seco.com/seco-ne/
kernel/linux-guf/-/commit/bc113aef63149d38a61f618b40f91e22d53fe5cd on the i.MX6
kernel.

Note: Replaced all occurences of the old G&F name to SECO and also fixed
some smaller typos.

BCS 746-000951