[ALSA] ASoC WM9712 kmemdup

This patch creates the WM9712 codec register cache using kmemdup instead
of doing a kzalloc followed by a memcpy.

Signed-off-by: Graeme Gregory <gg@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>