serial: max310x: Correction of the initial setting of the MODE1 bits for various supported ICs.

The MODE1 register bits have different values for different ICs.
This patch corrects the initial setting of this register in accordance
with the datasheets, which will allow you to get the expected values
when debugging the driver.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>