ASoC: cs42l52: Remove duplicate inclusion of slab.h header file

slab.h header file was included twice.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/cs42l52.c

@@ -24,7 +24,6 @@
 #include <linux/slab.h>
 #include <linux/workqueue.h>
 #include <linux/platform_device.h>
-#include <linux/slab.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>