uboot-phytec

rockchip: rk3399: Move u-boot, dm-pre-reloc of uart0, uart2

u-boot,dm-pre-reloc for uart0, uart2 indeed u-boot specific
properties. Move them into rk3399-u-boot.dtsi so the boards
which enabled these node will available during SPL.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>