The driver knows internally when a fan is not connected,
but does not export this knowledge to userspace. Use the
standard fanX_fault attributes to notify userspace if a
fan is not connected.

Tested on a Fujitsu DS3401-B1.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20230105225107.58308-4-W_Armin@gmx.deSigned-off-by: Guenter Roeck <linux@roeck-us.net>