ASoC: Intel: hda_dsp_common: use static function in conditional block

cppcheck reports the following warning:

sound/soc/intel/boards/hda_dsp_common.c:17:0: style: The function
'hda_dsp_hdmi_pcm_handle' is never used. [unusedFunction]

Fix by moving to static inside compilation block.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Jaska Uimonen <jaska.uimonen@intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20200923072939.3100468-1-kai.vehmanen@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>