cxl/region: Fix memregion leaks in devm_cxl_add_region()

Move the mode verification to __create_region() before allocating the
memregion to avoid the memregion leaks.

Fixes: 6e099264 ("cxl/region: Add volatile region creation support")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20240507053421.456439-1-lizhijian@fujitsu.comSigned-off-by: Dave Jiang <dave.jiang@intel.com>

drivers/cxl/core/region.c

@@ -2352,15 +2352,6 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
 	struct device *dev;
 	int rc;
 
-	switch (mode) {
-	case CXL_DECODER_RAM:
-	case CXL_DECODER_PMEM:
-		break;
-	default:
-		dev_err(&cxlrd->cxlsd.cxld.dev, "unsupported mode %d\n", mode);
-		return ERR_PTR(-EINVAL);
-	}
-
 	cxlr = cxl_region_alloc(cxlrd, id);
 	if (IS_ERR(cxlr))
 		return cxlr;
@@ -2415,6 +2406,15 @@ static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
 {
 	int rc;
 
+	switch (mode) {
+	case CXL_DECODER_RAM:
+	case CXL_DECODER_PMEM:
+		break;
+	default:
+		dev_err(&cxlrd->cxlsd.cxld.dev, "unsupported mode %d\n", mode);
+		return ERR_PTR(-EINVAL);
+	}
+
 	rc = memregion_alloc(GFP_KERNEL);
 	if (rc < 0)
 		return ERR_PTR(rc);