Support SPRAM Framebuffer

[WillGreen]

Add iCE40 SPRAM support for the new framebuffer design.

Current demos for iCEBreaker use BRAM, which restricts them to 160x90 in 4 colours. With SPRAM, iCEBreaker could support 320x180 in 16 colours as used on other boards.

[peepo]

had you some code to share?
I'm struggling with maskwren, examples in the wild are hard to find...
https://projectf.io/posts/spram-ice40-fpga/
makes a start, but....
tx

[WillGreen]

had you some code to share?

Not yet, but I plan to work on this in February.
I'll update this issue when I have a design to share.