serial/uart_ns16500: poll THRE to determine when data can be written

TEMT is Transmitter Empty bit which is set only when the full FIFO
is empty. It makes sense to poll for THRE (Transmitter Holding
Register Empty) which is set when UART can buffer new character
for transmission (there is room in FIFO). This allows using the
FIFO in full.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>

drivers/serial/uart_ns16550.c

@@ -401,7 +401,7 @@ static unsigned char uart_ns16550_poll_out(struct device *dev,
 					   unsigned char c)
 {
 	/* wait for transmitter to ready to accept a character */
-	while ((INBYTE(LSR(dev)) & LSR_TEMT) == 0)
+	while ((INBYTE(LSR(dev)) & LSR_THRE) == 0)
 		;
 
 	OUTBYTE(THR(dev), c);