Revert "functionfs: fix the open/removal races"

Revert "functionfs: fix the open/removal races"

This reverts commit b49c766856fb5901490de577e046149ebf15e39d which is
commit e5bf5ee266633cb18fff6f98f0b7d59a62819eee upstream.

It has been reported to cause test problems in Android devices.  As the
other functionfs changes were not also backported at the same time,
something is out of sync.  So just revert this one for now and it can
come back in the future as a patch series if it is tested.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>