scsi: megaraid_sas: Use struct_size() in code related to struct MR_FW_RAID_MAP

Prefer struct_size() over open-coded versions of idiom:

	sizeof(struct-with-flex-array) + sizeof(type-of-flex-array) * count

where count is the max number of items the flexible array is supposed to
have.

Link: https://github.com/KSPP/linux/issues/160
Link: https://lore.kernel.org/r/1211398fb8f7ab332a93f4f8f1a63e8168dbd002.1660592640.git.gustavoars@kernel.orgReviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -5155,9 +5155,9 @@ static void megasas_update_ext_vd_details(struct megasas_instance *instance)
 		fusion->current_map_sz = ventura_map_sz;
 		fusion->max_map_sz = ventura_map_sz;
 	} else {
-		fusion->old_map_sz =  sizeof(struct MR_FW_RAID_MAP) +
-					(sizeof(struct MR_LD_SPAN_MAP) *
-					instance->fw_supported_vd_count);
+		fusion->old_map_sz =
+			struct_size((struct MR_FW_RAID_MAP *)0, ldSpanMap,
+				    instance->fw_supported_vd_count);
 		fusion->new_map_sz =  sizeof(struct MR_FW_RAID_MAP_EXT);
 
 		fusion->max_map_sz =

drivers/scsi/megaraid/megaraid_sas_fp.c

@@ -326,9 +326,9 @@ u8 MR_ValidateMapInfo(struct megasas_instance *instance, u64 map_id)
 	else if (instance->supportmax256vd)
 		expected_size = sizeof(struct MR_FW_RAID_MAP_EXT);
 	else
-		expected_size =
-			(sizeof(struct MR_FW_RAID_MAP) +
-			(sizeof(struct MR_LD_SPAN_MAP) * le16_to_cpu(pDrvRaidMap->ldCount)));
+		expected_size = struct_size((struct MR_FW_RAID_MAP *)0,
+					    ldSpanMap,
+					    le16_to_cpu(pDrvRaidMap->ldCount));
 
 	if (le32_to_cpu(pDrvRaidMap->totalSize) != expected_size) {
 		dev_dbg(&instance->pdev->dev, "megasas: map info structure size 0x%x",