ASoC: Define soc_init_dai_link() to wrap link intialization.

Define soc_init_dai_link() to wrap link initialization, to reuse it later
by snd_soc_instantiate_card() when adding new DAI links from topology in
component probing phase.

Move static func snd_soc_init_multicodec(), so that it can be reused by
soc_init_dai_link(). This saves adding a function declaration for
snd_soc_init_multicodec().

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>