dynamic_debug: fix undefined reference to `__netdev_printk'

Dynamic debug recently added support for netdev_printk.  It uses
__netdev_printk() to support this functionality.  However, when CONFIG_NET
is not set, we get the following error:

lib/built-in.o: In function `__dynamic_netdev_dbg':
(.text+0x9fda): undefined reference to `__netdev_printk'

Fix this by making the call to netdev_printk() contingent upon CONFIG_NET.
 We could have fixed this by defining netdev_printk() to a 'no-op' in the
!CONFIG_NET case.  However, this is not consistent with how the networking
layer uses netdev_printk.  For example, CONFIG_NET is not set,
netdev_printk() does not have a 'no-op' definition defined.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

lib/dynamic_debug.c

@@ -503,6 +503,8 @@ int __dynamic_dev_dbg(struct _ddebug *descriptor,
 }
 EXPORT_SYMBOL(__dynamic_dev_dbg);
 
+#ifdef CONFIG_NET
+
 int __dynamic_netdev_dbg(struct _ddebug *descriptor,
 		      const struct net_device *dev, const char *fmt, ...)
 {
@@ -524,6 +526,8 @@ int __dynamic_netdev_dbg(struct _ddebug *descriptor,
 }
 EXPORT_SYMBOL(__dynamic_netdev_dbg);
 
+#endif
+
 static __initdata char ddebug_setup_string[1024];
 static __init int ddebug_setup_query(char *str)
 {