The recent change for the PCM sync API forgot to export a new API
function that is currently used in emu10k1 driver.

This patch adds the missing export.

Fixes: d712c58c ("ALSA: pcm: optimize and clarify stream synchronization ID API")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407051343.1Sz8AKFt-lkp@intel.com/Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://patch.msgid.link/20240705063555.17220-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>