Fill in BufferSize in PXENV_GET_CACHED_INFO

src/interface/pxe/pxe_preboot.c

 	buffer = real_to_user ( get_cached_info->Buffer.segment,
 				get_cached_info->Buffer.offset );
 	copy_to_user ( buffer, 0, data, len );
+	get_cached_info->BufferSize = len;
 
 	free ( data );
 	get_cached_info->Status = PXENV_STATUS_SUCCESS;