ACPI: scan: Fix device object rescan in acpi_scan_clear_dep()

In general, acpi_bus_attach() can only be run safely under
acpi_scan_lock, but that lock cannot be acquired under
acpi_dep_list_lock, so make acpi_scan_clear_dep() schedule deferred
execution of acpi_bus_attach() under acpi_scan_lock instead of
calling it directly.

This also fixes a possible race between acpi_scan_clear_dep() and
device removal that might cause a device object that went away to
be accessed, because acpi_scan_clear_dep() is changed to acquire
a reference on the consumer device object.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>