[media] as3645a: Fix compilation by including slab.h

The as3645a driver calls kzalloc(). Include slab.h.
Reported-by: NFredrik Lingvall <fredrik.lingvall@gmail.com>
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/as3645a.c

@@ -29,6 +29,7 @@
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/slab.h>
 
 #include <media/as3645a.h>
 #include <media/v4l2-ctrls.h>