Documentation: admin-guide: Update i8k driver name

The driver should be called dell_smm_hwmon, i8k is only
an alias now.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220109214248.61759-2-W_Armin@gmx.de


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