The input clock for uart is too slow (25MHz) which introduces frequent data error on both receiving and transmitting even if the baudrate is 115200. Using high-speed can significantly solve this issue. Reviewed-by: Simon Glass <sjg@chromium.org> Tested-by: Daniel Golle <daniel@makrotopia.org> Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>