We just got a common helper for parsing the rs485 specific
device tree properties. Use it and drop the open coded parser.

Note that there is a small difference between the removed and the now
used implementation: The former cleared flags to 0 if rs485-rts-delay
was given, the common helper clears SER_RS485_RX_DURING_TX and
SER_RS485_ENABLED only but always which makes more sense.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
[ukleinek: point out semantic change in commit log]
Acked-by: NNicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: NRichard Genoud <richard.genoud@gmail.com>
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>