Fix boot_pages calculation for machines that don't have UMA_MD_SMALL_ALLOC.

Fix boot_pages calculation for machines that don't have UMA_MD_SMALL_ALLOC.

o Call uma_startup1() after initializing kmem, vmem and domains.
o Include 8 eight VM startup pages into uma_startup_count() calculation.
o Account for vmem_startup() and vm_map_startup() preallocating pages.
o Account for extra two allocations done by kmem_init() and vmem_create().
o Hardcode the place of execution of vm_radix_reserve_kva(). Using SYSINIT
  allowed several other SYSINITs to sneak in before it, thus bumping
  requirement for amount of boot pages.