ASoC: topology: modify dapm route loading routine and add dapm route unloading

struct snd_soc_dapm_route has been modified to be a dynamic
object so that it can be used to save driver specific
data while parsing topology and clean up
driver-specific data during driver unloading.

This patch makes the following changes to accomplish the above:
1. Set the dobj member of snd_soc_dapm_route during the
SOC_TPLG_PASS_GRAPH pass of topology parsing.
2. Add the remove_route() routine that will be called while
removing all dynamic objects from the component driver.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>