arm64: dts: mediatek: mt8173-elm: remove panel model number in DT

Currently a specific panel number is used in the Elm DTSI, which is
corresponded to a 12" panel. However, according to the official Chrome
OS devices document, Elm refers to Acer Chromebook R13, which, as the
name specifies, uses a 13.3" panel, which comes with EDID information.

As the kernel currently prioritizes the hardcoded timing parameters
matched with the panel number compatible, a wrong timing will be applied
to the 13.3" panel on Acer Chromebook R13, which leads to blank display.

Because the Elm DTSI is shared with Hana board, and Hana corresponds to
multiple devices from 11" to 14", a certain panel model number shouldn't
be present, and driving the panel according to its EDID information is
necessary.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230526100801.16310-1-uwu@icenowy.me


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>