cxl/region: Fix IS_ERR() vs NULL check

The nvdimm_pmem_region_create() function returns NULL on error.  It does
not return error pointers.

Fixes: 04ad63f0 ("cxl/region: Introduce cxl_pmem_region objects")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/Yuo65lq2WtfdGJ0X@kiliSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/pmem.c

@@ -525,8 +525,8 @@ static int cxl_pmem_region_probe(struct device *dev)
 
 	cxlr_pmem->nd_region =
 		nvdimm_pmem_region_create(cxl_nvb->nvdimm_bus, &ndr_desc);
-	if (IS_ERR(cxlr_pmem->nd_region)) {
-		rc = PTR_ERR(cxlr_pmem->nd_region);
+	if (!cxlr_pmem->nd_region) {
+		rc = -ENOMEM;
 		goto err;
 	}