fpga: dfl: Use struct_size() in kzalloc()

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes. Also, remove unnecessary
function dfl_feature_platform_data_size().

This code was detected with the help of Coccinelle and, audited and
fixed manually.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

drivers/fpga/dfl.c

@@ -487,8 +487,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 	 * it will be automatically freed by device's release() callback,
 	 * platform_device_release().
 	 */
-	pdata = kzalloc(dfl_feature_platform_data_size(binfo->feature_num),
-			GFP_KERNEL);
+	pdata = kzalloc(struct_size(pdata, features, binfo->feature_num), GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;
 

drivers/fpga/dfl.h

@@ -299,12 +299,6 @@ struct dfl_feature_ops {
 #define DFL_FPGA_FEATURE_DEV_FME		"dfl-fme"
 #define DFL_FPGA_FEATURE_DEV_PORT		"dfl-port"
 
-static inline int dfl_feature_platform_data_size(const int num)
-{
-	return sizeof(struct dfl_feature_platform_data) +
-		num * sizeof(struct dfl_feature);
-}
-
 void dfl_fpga_dev_feature_uinit(struct platform_device *pdev);
 int dfl_fpga_dev_feature_init(struct platform_device *pdev,
 			      struct dfl_feature_driver *feature_drvs);