serial: ar933x: Deassert Transmit Enable on ->rs485_config()

stable inclusion
from stable-v5.10.154
commit 028fcabd8a67196277f907c8ecce8e0bb99b276a
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I64YCB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=028fcabd8a67196277f907c8ecce8e0bb99b276a



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

commit 3a939433 upstream.

The ar933x_uart driver neglects to deassert Transmit Enable when
->rs485_config() is invoked.  Fix it.

Fixes: 9be1064f ("serial: ar933x_uart: add RS485 support")
Cc: stable@vger.kernel.org # v5.7+
Cc: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Ilpo JÀrvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Lipeng Sang <sanglipeng1@jd.com>