ASoC: jack: Fix warning while make htmldocs caused by soc-jack.c

This patch fix following errors while "make htmldocs" on
linux-next-20141110.

Warning(.//sound/soc/soc-jack.c:126): No description found for
parameter 'zones'
Warning(.//sound/soc/soc-jack.c:126): Excess function parameter
'zone' description in 'snd_soc_jack_add_zones'

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>