cxl/test: Define a CFMWS capable of a 3 way HB interleave

The CXL unit test cxl-xor-region.sh is skipping a 1+1+1 region
interleave test case because the window is not defined.

Additionally, upcoming expansion of 3 way HB interleave test cases
(like 2+2+2) require the same window.

Replace an unused CFMWS with a 3-way capable CFMWS in the set of
CFMWS's loaded when interleave_arithmetic=1.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com>
Link: https://patch.msgid.link/20250226221931.2352061-1-alison.schofield@intel.com


Signed-off-by: Dave Jiang <dave.jiang@intel.com>