docs: hwmon: adm1177.rst: avoid using ReSt :doc:`foo` markup

The :doc:`foo` tag is auto-generated via automarkup.py.
So, use the filename at the sources, instead of :doc:`foo`.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/32b0db7e79a3ed0e817213113c607a1b819e3867.1622898327.git.mchehab+huawei@kernel.org


Signed-off-by: Guenter Roeck <linux@roeck-us.net>