dt-bindings: arm: samsung: Document E850-96 board binding

Add binding for the WinLink E850-96 board, which is based on Samsung
Exynos850 SoC.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20211217161549.24836-5-semen.protsenko@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>