docs: w1: w1_therm: Fix broken xref, mistakes, clarify text

sysfs attribute names are mixed with the same normal text terms.
Use ReST to distinguish.

Fix typos and mistakes.

Reported-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Ivan Zaentsev <ivan.zaentsev@wirenboard.ru>
Link: https://lore.kernel.org/r/20201008054259.5461-1-ivan.zaentsev@wirenboard.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>