serial: xilinx_uartps: unset STOPBRK when setting STARTBRK

Zynq UG585 states, in chapter B.33, for XUARTPS_CR_STARTBRK:
It can only be set if STPBRK (Stop transmitter break) is not high

This fixes tcsendbreak, which otherwise does not actually break.
Signed-Off-By: Julien Malik <julien.malik@unseenlabs.fr>
Link: https://lore.kernel.org/r/20230624210323.88455-1-julien.malik@unseenlabs.frSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/xilinx_uartps.c

@@ -657,7 +657,7 @@ static void cdns_uart_break_ctl(struct uart_port *port, int ctl)
 	status = readl(port->membase + CDNS_UART_CR);
 
 	if (ctl == -1)
-		writel(CDNS_UART_CR_STARTBRK | status,
+		writel(CDNS_UART_CR_STARTBRK | (~CDNS_UART_CR_STOPBRK & status),
 				port->membase + CDNS_UART_CR);
 	else {
 		if ((status & CDNS_UART_CR_STOPBRK) == 0)