ASoC: nau8825: fix static check error about semaphone control

The patch is to fix the static check error as the following.

The patch commit b50455fab459 ("ASoC: nau8825: cross talk suppression
measurement function") from Jun 7, 2016, leads to the following
static checker warning:

	sound/soc/codecs/nau8825.c:265 nau8825_sema_acquire()
	warn: 'sem:&nau8825->xtalk_sem' is sometimes locked here and
	sometimes unlocked.

The semaphone acquire function has return value, and some callers
can do error handling when lock fails.

Signed-off-by: John Hsu <KCHSU0@nuvoton.com>
Signed-off-by: Mark Brown <broonie@kernel.org>