tegra114: dalmore: fdt: enable dalmore SPI controller

Dalmore has a SPI flash part attached to controller 4, so enable
controller 4 and set to 25MHz.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>