serial: 8250_exar: Fill in rs485_supported

[ Upstream commit 59c221f8

 ]

Add information on supported serial_rs485 features.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606100433.13793-8-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 0c2a5f47

 ("serial: 8250_exar: Set missing rs485_supported flag")
Signed-off-by: Sasha Levin <sashal@kernel.org>