platform/x86: dell: Make DELL_WMI_PRIVACY depend on DELL_WMI

DELL_WMI_PRIVACY is a feature toggle for the main dell-wmi driver,
so it must depend on the Kconfig option which enables the main
dell-wmi driver.

Fixes: 8af9fa37 ("platform/x86: dell-privacy: Add support for Dell hardware privacy")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20211011132338.407571-1-hdegoede@redhat.com