tty: create internal tty.h file

stable inclusion
from stable-v5.10.180
commit 6a392b806f185dc122761d17138ab3bdc74bb823
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8FC2O

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6a392b806f185dc122761d17138ab3bdc74bb823

--------------------------------

[ Upstream commit 98602c01 ]

There are a number of functions and #defines in include/linux/tty.h that
do not belong there as they are private to the tty core code.

Create an initial drivers/tty/tty.h file and copy the odd "tty logging"
macros into it to seed the file with some initial things that we know
nothing outside of the tty core should be calling.

Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-2-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>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>