cxl/region: Constify cxl_region_resource_contains()

cxl/region: Constify cxl_region_resource_contains()

The call to cxl_region_resource_contains() in hmem_register_cxl_device()
need not cast away 'const'. The problem is the usage of the
bus_for_each_dev() API which does not mark its @data parameter as 'const'.
Switch to bus_find_device() which does take 'const' @data, fixup
cxl_region_resource_contains() and its caller.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260327052821.440749-5-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>