cxl/pmem: Use size_add() against integer overflow

"struct_size() + n" may cause a integer overflow,
use size_add() to handle it.
Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
Link: https://lore.kernel.org/r/20220927070247.23148-1-yuzhe@nfschina.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/pmem.c

@@ -148,7 +148,7 @@ static int cxl_pmem_set_config_data(struct cxl_dev_state *cxlds,
 		return -EINVAL;
 
 	/* 4-byte status follows the input data in the payload */
-	if (struct_size(cmd, in_buf, cmd->in_length) + 4 > buf_len)
+	if (size_add(struct_size(cmd, in_buf, cmd->in_length), 4) > buf_len)
 		return -EINVAL;
 
 	set_lsa =