x86: have set_memory_array_{uc,wb} coalesce memtypes.

Actually, might as well simply reconstruct the memtype list at free time
I guess. How is this for a coalescing version of the array functions?

Compiles, boots and provides me with:

  root@7ixe4:~# wc -l /debug/x86/pat_memtype_list
  53 /debug/x86/pat_memtype_list

otherwise (down from 16384+).

Signed-off-by: Ingo Molnar <mingo@elte.hu>