topology: Add element ID so we can look up references by name.

topology: Add element ID so we can look up references by name.

Add support to lookup elements by name. This is in preparation for adding
some new API calls that will allow building topology data using a C API. This
will allow applications to build their own topology data directly.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>