fpga-manager: altera-ps-spi: preserve nCONFIG state

If the driver module is loaded when FPGA is configured, the FPGA
is reset because nconfig is pulled low (low-active gpio inited
with GPIOD_OUT_HIGH activates the signal which means setting its
value to low). Init nconfig with GPIOD_OUT_LOW to prevent this.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Cc: stable <stable@vger.kernel.org> # 4.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>