serial: fix serial_txx9.c build warning/typo

From: Randy Dunlap <redacted>

Fix kconfig symbol test to use "defined":

drivers/tty/serial/serial_txx9.c: warning: "CONFIG_CONSOLE_POLL" is not defined [-Wundef]

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Randy Dunlap <redacted>
---
 drivers/tty/serial/serial_txx9.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- lnx-35-rc1.orig/drivers/tty/serial/serial_txx9.c
+++ lnx-35-rc1/drivers/tty/serial/serial_txx9.c

@@ -466,7 +466,7 @@ static void serial_txx9_break_ctl(struct
 	spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
-#if defined(CONFIG_SERIAL_TXX9_CONSOLE) || (CONFIG_CONSOLE_POLL)
+#if defined(CONFIG_SERIAL_TXX9_CONSOLE) || defined(CONFIG_CONSOLE_POLL)
 /*
  *	Wait for transmitter & holding register to empty
  */