tm32_uart_dma.h : fixed bug in UartIrqHandler().
tm32_uart_dma.h : fixed bug in UartIrqHandler().

At STM32L0XX chip USART transmission complete interrupt flag is
cleared by writing 1 to dedicated bit in "interrupt clear register".
(Other chips uses sequence "read data register - read status register")

antongus/stm32tpl,antongus/stm32tpl