ASoC: Intel: fix possible acpi enumeration panic

A crash can occur on some platforms where adsp is enumerated but codec is not
matched. Define codec_id as a pointer intead of an array so that it gets
initialized to NULL for the terminating element of sst_acpi_bytcr[] and
sst_acpi_chv[].

Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>