ASoC: soc-core: use GFP_KERNEL flag for kmalloc in snd_soc_cnew

GFP_ATOMIC is not needed here, use GFP_KERNEL instead.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>