net-caif: using kmalloc/kfree requires the include of slab.h

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/caif/cfcnfg.c

@@ -5,6 +5,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/stddef.h>
+#include <linux/slab.h>
 #include <net/caif/caif_layer.h>
 #include <net/caif/cfpkt.h>
 #include <net/caif/cfcnfg.h>