cifs: silence compiler warnings showing up with gcc-8.0.0

This bug was fixed before, but came up again with the latest
compiler in another function:

fs/cifs/cifssmb.c: In function 'CIFSSMBSetEA':
fs/cifs/cifssmb.c:6362:3: error: 'strncpy' offset 8 is out of the bounds [0, 4] [-Werror=array-bounds]
   strncpy(parm_data->list[0].name, ea_name, name_len);

Let's apply the same fix that was used for the other instances.

Fixes: b2a3ad9c ("cifs: silence compiler warnings showing up with gcc-4.7.0")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NSteve French <smfrench@gmail.com>

fs/cifs/cifssmb.c

@@ -6343,9 +6343,7 @@ CIFSSMBSetEA(const unsigned int xid, struct cifs_tcon *tcon,
 	pSMB->InformationLevel =
 		cpu_to_le16(SMB_SET_FILE_EA);
 
-	parm_data =
-		(struct fealist *) (((char *) &pSMB->hdr.Protocol) +
-				       offset);
+	parm_data = (void *)pSMB + offsetof(struct smb_hdr, Protocol) + offset;
 	pSMB->ParameterOffset = cpu_to_le16(param_offset);
 	pSMB->DataOffset = cpu_to_le16(offset);
 	pSMB->SetupCount = 1;