w1: add helper macro module_w1_family

The helper macro module_w1_family can be used in module drivers that
only register a w1 driver in their module init functions.  Add this
macro and use it in all applicable drivers.

Link: http://lkml.kernel.org/r/20160531204313.20979-2-afd@ti.com
Signed-off-by: Andrew F. Davis <afd@ti.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/w1/slaves/w1_ds2408.c b/drivers/w1/slaves/w1_ds2408.c
index 7dfa0e1..aec5958 100644
--- a/drivers/w1/slaves/w1_ds2408.c
+++ b/drivers/w1/slaves/w1_ds2408.c
@@ -351,16 +351,4 @@
 	.fid = W1_FAMILY_DS2408,
 	.fops = &w1_f29_fops,
 };
-
-static int __init w1_f29_init(void)
-{
-	return w1_register_family(&w1_family_29);
-}
-
-static void __exit w1_f29_exit(void)
-{
-	w1_unregister_family(&w1_family_29);
-}
-
-module_init(w1_f29_init);
-module_exit(w1_f29_exit);
+module_w1_family(w1_family_29);