Add the missing description for the new parameter "start" of
snd_hdac_stream_timecounter_init() in the previous patch.

Fixes: df521561 ("ALSA: hda: fix trigger_tstamp_latched")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410031300.ecLmATNd-lkp@intel.com/
Link: https://patch.msgid.link/20241003072420.8932-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>