boards: Update MIMXRT685 to pass SPI DMA channel number
boards: Update MIMXRT685 to pass SPI DMA channel number

The DMA TX and RX channel numbers are used when
CONFIG_SPI_MCUX_FLEXCOMM_DMA is enabled

Signed-off-by: Mahesh Mahadevan <7f315ec3481825d543f8bec256ad86a4adc9dd8a@nxp.com>

nashif/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr