platform/x86: dell-wmi-sysman: Make sysman_init() return -ENODEV of the interfaces are not found

When either the attributes or the password interface is not found, then
unregister the 2 wmi drivers again and return -ENODEV from sysman_init().

Fixes: e8a60aa7

 ("platform/x86: Introduce support for Systems Management Driver over WMI for Dell Systems")
Cc: Divya Bharathi <Divya_Bharathi@dell.com>
Cc: Mario Limonciello <mario.limonciello@dell.com>
Reported-by: Alexander Naumann <alexandernaumann@gmx.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210321115901.35072-7-hdegoede@redhat.com