net: cgroups: fix build errors when linux/phy*.h is removed from net/dsa.h

net/core/netprio_cgroup.c:303:16: error: expected declaration specifiers or '...' before string constant
    MODULE_LICENSE("GPL v2");
                   ^~~~~~~~

Add linux/module.h to fix this.
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/netprio_cgroup.c

@@ -13,6 +13,7 @@
 
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/module.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/skbuff.h>