MAINTAINERS: Add lib/net_utils.c to NETWORKING (general)

It looks like the best place in MAINTAINERS data base to cover this
orphaned module.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -9438,6 +9438,7 @@ F:	include/uapi/linux/net.h
 F:	include/uapi/linux/netdevice.h
 F:	include/uapi/linux/net_namespace.h
 F:	tools/testing/selftests/net/
+F:	lib/net_utils.c
 F:	lib/random32.c
 
 NETWORKING [IPSEC]