topology: Make buffer for saving dynamic size

topology: Make buffer for saving dynamic size

Some fields can exceed size limit, e.g. private data has no size
restriction. Therefore it needs to be dynamically increased.

Signed-off-by: Piotr Maziarz <piotrx.maziarz@linux.intel.com>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Reviewed-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>