Add Address remapping (build time).
Address space remapping
move dram -> 0x0, rom -> 0x400000, sram->0x41000000 and reset address to start of rom.
This will require changes in the following other repos:
https://gitlab.raptorengineering.com/kestrel-collaboration/kestrel-litex/litex/-/merge_requests/2
https://gitlab.raptorengineering.com/kestrel-collaboration/bootrom/-/merge_requests/16