Revert "tty: tty_port: add workqueue to flip TTY buffer"

Revert "tty: tty_port: add workqueue to flip TTY buffer"

This reverts commit d000422a46aad32217cf1be747eb61d641baae2f.

It is reported by many to cause boot failures, so must be reverted.

Cc: Xin Zhao <jackzxcui1989@163.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/d1942304-ee30-478d-90fb-279519f3ae81@samsung.com
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reported-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>