thermal: sysfs-api.txt - reformat for improved readability

The document currently uses large indentations which make the text
too wide for easy readability. Also improve general consistency.

Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>