arm: mvebu: turris_mox: Fix early SPI communication

The SPI clock signal changes value when the SPI configuration register
is configured. This can sometimes lead to the device misinterpreting
the enablement of the SPI controller as actual clock tick.
This can be solved by first setting the SPI CS1 pin from GPIO to SPI mode,
and only after that writing the SPI configuration register.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>