ARM: dts: rockchip: enable DMA on SPI for rk3066 and rk3188

According to the RK3066 and RK3188 TRM, the two SPI controllers support DMA
handshake interface. Add the DMA properties so they can be used when needed.

Signed-off-by: Julien CHAUVEAU <julien.chauveau@neo-technologies.fr>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>