topology: Define a function to build a single physical DAI link

topology: Define a function to build a single physical DAI link

Code refactoring. Rename the function to build all physical links from
tplg_build_link_config() to tplg_build_links(). And define a new function
build_link() to build a single physical DAI link element.

The function build_link() will be extended to handle more properties
of a physical DAI link (e.g. backend or codec-codec link).

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