[ALSA] Remove trailing white space from wm9712.c

This patch removes some trailing white space from the WM9712 ASoC codec
driver.
Signed-off-by: NLiam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@suse.cz>