w1_therm: adding code comments and code reordering

commit  54043331eaabe6f3c3ce553bc902838d4153812d from
https://github.com/raspberrypi/linux.git rpi-5.4.y

commit 92b8d272

 upstream.

Adding code comments to split code in dedicated parts. After the global
declarations (defines, macros and function declarations), code is organized
as follow :
 - Device and family dependent structures and functions
 - Interfaces functions
 - Helpers functions
 - Hardware functions
 - Sysfs interface functions

Signed-off-by: Akira Shimahara <akira215corp@gmail.com>
Link: https://lore.kernel.org/r/20200511203535.409599-1-akira215corp@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Meng Li <Meng.Li@windriver.com>