drm/panel: Add support for Armadeus ST0700 Adapt

This patch adds support for the Armadeus ST0700 Adapt. It comes with a
Santek ST0700I5Y-RBSLW 7.0" WVGA (800x480) TFT and an adapter board so
that it can be connected on the TFT header of Armadeus Dev boards.

Cc: stable@vger.kernel.org # v4.19
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190507152713.27494-1-sebastien.szymanski@armadeus.com