tty/hvc_console: Add DTR/RTS callback to handle HUPCL control

Introduce a new callback to explicitly handle the HUPCL termios control flag.
This prepares for a follow-up commit for the hvc_iucv device driver to
improve handling when to drop an established network connection.

The callback naming is based on the recently added tty_port interface to
facilitate a potential refactoring of the hvc_console to use tty_port
functions.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/hvc/hvc_console.h

@@ -75,6 +75,9 @@ struct hv_ops {
 	/* tiocmget/set implementation */
 	int (*tiocmget)(struct hvc_struct *hp);
 	int (*tiocmset)(struct hvc_struct *hp, unsigned int set, unsigned int clear);
+
+	/* Callbacks to handle tty ports */
+	void (*dtr_rts)(struct hvc_struct *hp, int raise);
 };
 
 /* Register a vterm and a slot index for use as a console (console_init) */