ARM: dts: vf610-bk4: Provide support for reading ID code from MVB device

The procedure to read this ID value is as follows:

rmmod spi_fsl_dspi
insmod spi-gpio.ko

echo 504 > /sys/class/gpio/export
cat /sys/class/gpio/gpio504/value
...
echo 511 > /sys/class/gpio/export
cat /sys/class/gpio/gpio511/value

rmmod spi-gpio.ko
insmod spi_fsl_dspi

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>