rk3399: boot_devices fix spinor node name

Problem: board_spl_was_booted_from return wrong boot_devices[3] value
/spi@ff1d0000 and same-as-spl dont work properly for SPINOR flash
because arch/arm/mach-rockchip/spl-boot-order.c spl_node_to_boot_device
need parse SPINOR flash node as UCLASS_SPI_FLASH

spl-boot-order: same-as-spl > *** BOOT_SOURCE_ID 3 (2:emmc 3:spi 5:sd ...
/spi@ff1d0000 > board_boot_order: could not map node @618 to a boot-device
/sdhci@fe330000 > /mmc@fe320000

Solution: just change it to /spi@ff1d0000/flash@0

spl-boot-order: same-as-spl > *** BOOT_SOURCE_ID 3 (2:emmc 3:spi 5:sd ...
/spi@ff1d0000/flash@0 > /sdhci@fe330000 > /mmc@fe320000

Signed-off-by: Artem Lapkin <art@khadas.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>