pch_uart: remove set but not used variable 'tx_empty'

tx_empty is not used after setting its value. It is safe to remove
the unused variable.

Signed-off-by: zhong jiang <[e-mail]>
Reviewed-by: Jiri Slaby <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/pch_uart.c

···
 	struct scatterlist *sg;
 	int nent;
 	int fifo_size;
-	int tx_empty;
 	struct dma_async_tx_descriptor *desc;
 	int num;
 	int i;
···
 	}
 
 	fifo_size = max(priv->fifo_size, 1);
-	tx_empty = 1;
 	if (pop_tx_x(priv, xmit->buf)) {
 		pch_uart_hal_write(priv, xmit->buf, 1);
 		port->icount.tx++;
-		tx_empty = 0;
 		fifo_size--;
 	}