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>