Split code_800D31A0.c into sys_freeze.c and sys_debug_controller.c

[cadmic]

I kinda think these are two separate files since half of it is debug-only, and it's not that related to the other half.

[hensldm]

Out of curiosity any thoughts on the name for func_800D31A0. I was thinking something like just Freeze or Freeze_Forever? For reference we have an open PR in MM to rename the file and function (though I agree with sys_freeze for the file name vs the sleep_forever in that PR).

[cadmic]

Oh, I didn't think to check open MM PRs, thanks. IMO Freeze_Forever sounds redundant, so if Freeze is not specific enough then maybe we can say what is being frozen (something like FreezeCpu?)