w1: Organize driver source to natural/common order

Structures and functions should be ordered such that forward declaration
use is minimized.

MODULE_* macros should immediately follow the structures and functions
upon which they act.

Remaining MODULE_* macros should be at the end of the file in
alphabetical order.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>