wifi: brcmfmac: Use struct_size() in code ralated to struct brcmf_dload_data_le

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

sizeof(struct-with-flex-array) + sizeof(typeof-flex-array-elements) * count

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

In this particular case, in the open-coded version sizeof(typeof-flex-array-elements)
is implicit in _count_ because the type of the flex array data is u8:

drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h:941:
 941 struct brcmf_dload_data_le {
 942         __le16 flag;
 943         __le16 dload_type;
 944         __le32 len;
 945         __le32 crc;
 946         u8 data[];
 947 };

Link: https://github.com/KSPP/linux/issues/160Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/41845ad3660ed4375f0c03fd36a67b2e12fafed5.1668548907.git.gustavoars@kernel.org

drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c

@@ -110,9 +110,9 @@ static int brcmf_c_download(struct brcmf_if *ifp, u16 flag,
 	dload_buf->dload_type = cpu_to_le16(DL_TYPE_CLM);
 	dload_buf->len = cpu_to_le32(len);
 	dload_buf->crc = cpu_to_le32(0);
-	len = sizeof(*dload_buf) + len;
 
-	err = brcmf_fil_iovar_data_set(ifp, "clmload", dload_buf, len);
+	err = brcmf_fil_iovar_data_set(ifp, "clmload", dload_buf,
+				       struct_size(dload_buf, data, len));
 
 	return err;
 }
@@ -139,7 +139,8 @@ static int brcmf_c_process_clm_blob(struct brcmf_if *ifp)
 		return 0;
 	}
 
-	chunk_buf = kzalloc(sizeof(*chunk_buf) + MAX_CHUNK_LEN, GFP_KERNEL);
+	chunk_buf = kzalloc(struct_size(chunk_buf, data, MAX_CHUNK_LEN),
+			    GFP_KERNEL);
 	if (!chunk_buf) {
 		err = -ENOMEM;
 		goto done;