Migrate all the "u-boot,dm-pre-reloc" tag from rk3288-tinker.dts
into rk3288-tinker-u-boot.dtsi.
When both board level and soc level '-u-boot.dtsi' files exist,
we need to include the soc level 'rk3288-u-boot.dtsi' manually.
Signed-off-by: NKever Yang <kever.yang@rock-chips.com>