Add 8250 UART APDMA to support MediaTek UART. If MediaTek UART is
enabled by SERIAL_8250_MT6577, and we can enable this driver to offload
the UART device moving bytes.
Signed-off-by: Long Cheng <long.cheng@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>