The only caller of acpi_scan_init(), acpi_init(), doesn't check its
return value, so turn it into a void function.

This avoids complaints from the Smatch static checker that the
function should return a negative error code when it fails, which
is not really a problem in this particular case.

No intentional functional impact.

Link: https://lore.kernel.org/linux-acpi/20220106082317.GA9123@kili/Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>