ASoC: Intel: Skylake: Get node id using helper

skl_setup_cpr_gateway_cfg() retrieves gateway settings which are
required for copier module configuration. For upcoming DMA
control IPC we need similar retrieval, so separate this piece into
skl_get_node_id() helper which will be common for these functions

Signed-off-by: Dharageswari R <dharageswari.r@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>