cxl/test: Adjust the mock version of devm_cxl_switch_port_decoders_setup()

cxl/test: Adjust the mock version of devm_cxl_switch_port_decoders_setup()

With devm_cxl_switch_port_decoders_setup() being called within cxl_core
instead of by the port driver probe, adjustments are needed to deal with
circular symbol dependency when this function is being mock'd. Add the
appropriate changes to get around the circular dependency.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>