hwmon: (hp-wmi-sensors) Get WMI instance count from WMI driver core

Commit 2a2b13ae ("platform/x86: wmi: Allow retrieving the number of
WMI object instances") means we no longer need to find this ourselves.

Signed-off-by: James Seo <james@equiv.tech>
Link: https://lore.kernel.org/r/20230722172513.9324-2-james@equiv.tech


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