r8169: simplify setting hwmon attribute visibility

Use new member visible to simplify setting the static visibility.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/dba77e76-be45-4a30-96c7-45e284072ad2@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>