Get emulation of video output / framebuffer working.

[Tim 'mithro' Ansell]

It's just "read from this memory" type thing.

Registers set video resolution + where to read from.

[Tim 'mithro' Ansell]

For EDID -> https://github.com/timvideos/qemu-litex/blob/master/hw/i2c/i2c-ddc.c