tty: fix typo in ASYNCB_FOURPORT comment

On #define ASYNCB_FOURPORT there's an ortography error on comment:
"Set OU1, OUT2 per AST Fourport settings"

Change it into:
"Set OUT1, OUT2 per AST Fourport settings"
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/uapi/linux/tty_flags.h

@@ -13,7 +13,7 @@
  */
 #define ASYNCB_HUP_NOTIFY	 0 /* Notify getty on hangups and closes
 				    * on the callout port */
-#define ASYNCB_FOURPORT		 1 /* Set OU1, OUT2 per AST Fourport settings */
+#define ASYNCB_FOURPORT		 1 /* Set OUT1, OUT2 per AST Fourport settings */
 #define ASYNCB_SAK		 2 /* Secure Attention Key (Orange book) */
 #define ASYNCB_SPLIT_TERMIOS	 3 /* [x] Separate termios for dialin/callout */
 #define ASYNCB_SPD_HI		 4 /* Use 57600 instead of 38400 bps */