tty: TIOCGSOFTCAR/SSOFTCAR on pty is wron

The termios settings ioctls on a pty should affect the bound tty side not
the pty. The SOFTCAR ioctls use the wrong device file.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>