Revert "drivers:tty:pty: Fix a race causing data loss on close"

This reverts commit 33d4ae98.

Pierre-Louis writes:

	Our SOF/audio CI shows an across-the-board regression when we try v5.12-rc1,
	specifically on pause/resume tests with an interactive terminal running 'aplay
	-i' commands managed by expect to simulate the user pressing the space bar to
	pause/unpause. It turns out the processes are not longer killed and the audio
	devices remain busy (see publicly available test results listed below).

	git bisect points to commit 33d4ae98

 ("drivers:tty:pty: Fix a race
	causing data loss on close"). Reverting the patch fixes the issue on all test
	devices.

	Further analysis with Corey Minyard points to a problem where a slave tty will
	not get a SIGHUP when the master is closed.

So revert this for now:

Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/00154592-c5ee-aaba-956e-b265473b53bc@linux.intel.com
Cc: Corey Minyard <cminyard@mvista.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Mark Brown <broonie@kernel.org>,
Fixes: 33d4ae98

 ("drivers:tty:pty: Fix a race causing data loss on close")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>