serial: mtk: initial priv data before using

This patch ensures driver private data being fully initialized in
_debug_uart_init which is not covered by .priv_auto ops.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
Reviewed-by: Stefan Roese <sr@denx.de>
1 file changed