tty: move some internal tty lock enums and functions out of tty.h

[ Upstream commit 6c80c0b9 ]

Move the TTY_LOCK_* enums and tty_ldisc lock functions out of the global
tty.h into the local header file to clean things up.

Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-10-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 094fb49a ("tty: Prevent writing chars during tcsetattr TCSADRAIN/FLUSH")
Signed-off-by: Sasha Levin <sashal@kernel.org>