ASoC: update gfp/slab.h includes

Implicit slab.h inclusion via percpu.h is about to go away.  Make sure
gfp.h or slab.h is included as necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/soc/codecs/cq93vc.c b/sound/soc/codecs/cq93vc.c
index 5132974..8f19b93 100644
--- a/sound/soc/codecs/cq93vc.c
+++ b/sound/soc/codecs/cq93vc.c
@@ -27,6 +27,7 @@
 #include <linux/pm.h>
 #include <linux/platform_device.h>
 #include <linux/device.h>
+#include <linux/slab.h>
 #include <linux/clk.h>
 #include <linux/mfd/davinci_voicecodec.h>