No need to maintain a received byte count; we always fill in sequential

order so we can just use buffer->fill.

src/include/gpxe/ftp.h

 	char status_text[4];
 	/** Passive-mode parameters, as text */
 	char passive_text[24]; /* "aaa,bbb,ccc,ddd,eee,fff" */
-	/** Amount of data received */
-	size_t data_rcvd;
 
 	/** TCP application for the control channel */
 	struct tcp_application tcp;

src/net/tcp/ftp.c

 
 	/* Fill data buffer */
 	if ( ( rc = fill_buffer ( ftp->buffer, data,
-				  ftp->data_rcvd, len ) ) != 0 ){
+				  ftp->buffer->fill, len ) ) != 0 ){
 		DBGC ( ftp, "FTP %p failed to fill data buffer: %s\n",
 		       ftp, strerror ( rc ) );
 		ftp_done ( ftp, rc );
 		return;
 	}
-
-	/* Update received data total */
-	ftp->data_rcvd += len;
 }
 
 /** FTP data channel operations */
 	ftp->already_sent = 0;
 	ftp->recvbuf = ftp->status_text;
 	ftp->recvsize = sizeof ( ftp->status_text ) - 1;
-	ftp->data_rcvd = 0;
 	ftp->tcp.tcp_op = &ftp_tcp_operations;
 	ftp->tcp_data.tcp_op = &ftp_data_tcp_operations;
 	if ( ( rc = tcp_connect ( &ftp->tcp, &ftp->server, 0 ) ) != 0 )