cxl/mbox: Remove useless cast in cxl_mem_create_range_info()

DEFINE_RES_MEM() is a wrapper around the DEFINE_RES_NAMED() macro
which already has the (struct resource) for the compound literal.
The user of the macro should not repeat the cast.

Cleans up these sparse warnings:
drivers/cxl/core/mbox.c:1184:18: warning: cast to non-scalar
drivers/cxl/core/mbox.c:1184:18: warning: cast from non-scalar

Fixes: 52c4d11f ("resource: Convert DEFINE_RES_NAMED() to be compound literal")
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230815172052.22514-1-alison.schofield@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -1224,8 +1224,7 @@ int cxl_mem_create_range_info(struct cxl_memdev_state *mds)
 		return 0;
 	}
 
-	cxlds->dpa_res =
-		(struct resource)DEFINE_RES_MEM(0, mds->total_bytes);
+	cxlds->dpa_res = DEFINE_RES_MEM(0, mds->total_bytes);
 
 	if (mds->partition_align_bytes == 0) {
 		rc = add_dpa_res(dev, &cxlds->dpa_res, &cxlds->ram_res, 0,