x86: PAT use reserve free memtype in ioremap and iounmap

Use reserve_memtype and free_memtype interfaces in ioremap/iounmap to avoid
aliasing.

If there is an existing alias for the region, inherit the memory type from
the alias. If there are conflicting aliases for the entire region, then fail
ioremap.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>