```
Do not preallocate pcpu area backing pages on early startup, only
allocate enough of KVA for pcpu[MAXCPU] and the page for BSP. Other
pages are allocated after we know the number of cpus and their
assignments to the domains.
PCPUs are not accessed until they are initialized, which happens on AP
startup.
```
```
amd64: initialize APs kpmap_store in init_secondary()
The APs pcpu area is zeroed in init_secondary() by pcpu_init(), so the
early initialization in pmap_bootstrap() is nop.
Fixes: 42f722e721cd010ae5759a4b0d3b7b93c2b9cad2
```