ksmbd: Remove a redundant zeroing of memory

fill_transform_hdr() has only one caller that already clears tr_buf (it is
kzalloc'ed).

So there is no need to clear it another time here.

Remove the superfluous memset() and add a comment to remind that the caller
must clear the buffer.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Hyunchul Lee <hyc.lee@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -8500,7 +8500,7 @@ static void fill_transform_hdr(void *tr_buf, char *old_buf, __le16 cipher_type)
 	struct smb2_hdr *hdr = smb2_get_msg(old_buf);
 	unsigned int orig_len = get_rfc1002_len(old_buf);
 
-	memset(tr_buf, 0, sizeof(struct smb2_transform_hdr) + 4);
+	/* tr_buf must be cleared by the caller */
 	tr_hdr->ProtocolId = SMB2_TRANSFORM_PROTO_NUM;
 	tr_hdr->OriginalMessageSize = cpu_to_le32(orig_len);
 	tr_hdr->Flags = cpu_to_le16(TRANSFORM_FLAG_ENCRYPTED);