get warmbooting working

Currenty, there is a warmbooting demo for the iCEStick HX1K, but the same code does not work for the UP5K.

This may be desirable for cases where we could load multiple images into flash and swap between them
https://github.com/evolvablehardware/ice40_memory_controller/tree/warmboot_demo

The value of this can be confirmed by measuring the time taken to swap between images. We have the ability to write all of the CRAM in ~25ms on the pico-ice board, but going even faster could be advantageous under some circumstances

See work done on this previously:
https://github.com/juanmard/screen-warmboot

As well as Allyn's notes from this summer:
https://github.com/evolvablehardware/pRNA_obsidian/blob/main/work_log_allyn/2025-08-07.md