Regions should have separate sizes for DTCM and SDRAM

[neworderofjamie]

Large recording regions are the extreme case of this as they can take several megabytes of SDRAM, but essentially no DTCM. I've made the following hack to the LIF constraints, but it's not the best solution:

constraints = {
            sdram_constraint: lambda s: regions.utils.sizeof_regions(
                self.regions, s),
            dtcm_constraint: lambda s: regions.utils.sizeof_regions(
                self.regions[:-2], s),  # **HACK**
            cpu_constraint: cpu_usage,
        }

[mundya]

Definitely agree.