cxl/region: Fix the first aliased address miscalculation

cxl/region: Fix the first aliased address miscalculation

In extended linear cache(ELC) case, cxl_port_get_spa_cache_alias() helps
to get the aliased address of a SPA, it considers the first address in
CXL memory range is "region start + region cache size + 1", but it
should be "region start + region cache size".

So if a SPA is equal to "region start + region cache size", its aliased
address should be "SPA - region cache size".

Signed-off-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://patch.msgid.link/20250317070124.815028-1-ming.li@zohomail.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>