cxl/region: Move HPA setup to cxl_region_attach()

A recent bug fix added the setup of the endpoint decoder interleave
geometry settings to cxl_region_attach(). Move the HPA setup there as
well to keep all endpoint decoder parameter setting in a central
location.

For symmetry, move endpoint HPA teardown to cxl_region_detach(), and for
switches move HPA setup / teardown to cxl_port_{setup,reset}_targets().

Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/165973126020.1526540.14701949254436069807.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>