tty: Make tty_termios_copy_hw() old ktermios const

There should be no reason to adjust old ktermios which is going to get
discarded anyway.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-5-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_ioctl.c

@@ -249,7 +249,7 @@ static void unset_locked_termios(struct tty_struct *tty, struct ktermios *old)
  *	in some cases where only minimal reconfiguration is supported
  */
 
-void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
+void tty_termios_copy_hw(struct ktermios *new, const struct ktermios *old)
 {
 	/* The bits a dumb device handles in software. Smart devices need
 	   to always provide a set_termios method */

include/linux/tty.h

@@ -458,7 +458,7 @@ static inline speed_t tty_get_baud_rate(struct tty_struct *tty)
 unsigned char tty_get_char_size(unsigned int cflag);
 unsigned char tty_get_frame_size(unsigned int cflag);
 
-void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old);
+void tty_termios_copy_hw(struct ktermios *new, const struct ktermios *old);
 int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b);
 int tty_set_termios(struct tty_struct *tty, struct ktermios *kt);