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_ds2781.c b/drivers/w1/slaves/w1_ds2781.c
index 99b0f4d..9c03e01 100644
--- a/drivers/w1/slaves/w1_ds2781.c
+++ b/drivers/w1/slaves/w1_ds2781.c
@@ -151,19 +151,7 @@
 	.fid = W1_FAMILY_DS2781,
 	.fops = &w1_ds2781_fops,
 };
-
-static int __init w1_ds2781_init(void)
-{
-	return w1_register_family(&w1_ds2781_family);
-}
-
-static void __exit w1_ds2781_exit(void)
-{
-	w1_unregister_family(&w1_ds2781_family);
-}
-
-module_init(w1_ds2781_init);
-module_exit(w1_ds2781_exit);
+module_w1_family(w1_ds2781_family);
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Renata Sayakhova <renata@oktetlabs.ru>");