intel: Size reduction of intel_perf from static reg tables

ChromeOS is concerned about an uprev of Mesa having added ~3MB to each of the vulkan and i965 drivers. Here's a little patch to fix part of the size increase (and some warning fixes that were driving me nuts)

https://bugs.chromium.org/p/chromium/issues/detail?id=1048434

@llandwerlin I'm not sure exactly how to test this code, could you verify it still works?