[media] smiapp-core: fix compilation build error

smiapp-core.c:2472:3: error: implicit declaration of function 'kzalloc' [-Werror=implicit-function-declaration]
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/smiapp/smiapp-core.c

@@ -31,6 +31,7 @@
 #include <linux/device.h>
 #include <linux/gpio.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 #include <linux/v4l2-mediabus.h>