arm64: dts: rockchip: Always enable DFI on rk3399

the DFI unit can provide useful data for measuring DDR utilization
and works without any configuration from the board, so enable it in the
dtsi file directly.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20231018061714.3553817-25-s.hauer@pengutronix.de


Signed-off-by: Heiko Stuebner <heiko@sntech.de>