dt-bindings: dma: mediatek,uart-dma: Add binding for MT6795 SoC

Add mediatek,mt6795-uart-dma to the compatibles list to support
the MT6795 Helio X10 SoC's UART APDMA.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220729104441.39177-2-angelogioacchino.delregno@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>