arm: dts: socfpga: Add u-boot, dm-pre-reloc for sysmgr and clkmgr nodes

Add u-boot,dm-pre-reloc for sysmgr and clkmgr nodes to use it in SPL.
In preparation to get base address from DT.

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>