Use per-CPU attributes earlier.

The per-CPU ts is not initialized early, so the global kernel ts is used
early, but it ony has 1 (normal) attribute. Switch this to the per-CPU
attribute.

The difference is most visible with EARLY_AP_STARTUP.

Change to using the curcpu macro instead of PCPU_GET(cpuid) in 2 places for
the above and in 1 other place in my old code in syscons. The function-like
spelling is perhaps better for indicating that curcpu is volatile (unlike
curthread), but for CPU attributes volatility is a feature.