Remove the unused function hsw_pcm_free_modules() to fix the
compling warning:

sound/soc/intel/haswell/sst-haswell-pcm.c:923:13:
 warning: 'sw_pcm_free_modules' defined but not used
 [-Wunused-function]
 static void hsw_pcm_free_modules(struct hsw_priv_data *pdata)
Signed-off-by: Jie Yang <yang.jie@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>