Revert "tty: fix port buffer locking"

This reverts commit 925bb1ce47f429f69aad35876df7ecd8c53deb7e.

It causes lots of warnings and problems so for now, let's just revert
it.

Reported-by: <[e-mail]>
Reported-by: Russell King <[e-mail]>
Reported-by: Sergey Senozhatsky <[e-mail]>
Reported-by: Geert Uytterhoeven <[e-mail]>
Reported-by: Jiri Slaby <[e-mail]>
Reported-by: Andrey Konovalov <[e-mail]>
Acked-by: Vegard Nossum <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/tty_port.c

···
 	if (!disc)
 		return 0;
 
-	mutex_lock(&tty->atomic_write_lock);
 	ret = tty_ldisc_receive_buf(disc, p, (char *)f, count);
-	mutex_unlock(&tty->atomic_write_lock);
 
 	tty_ldisc_deref(disc);