arm64: dts: meson: import libretech-pc from linux v5.6-rc2

Sync the libretech-pc device tree from Linux v5.6-rc2
11a48a5a18c6 ("Linux 5.6-rc2")

Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>