platform/surface: aggregator: Do not return uninitialized value

The status variable in ssam_nf_refcount_disable_free() is only set when
the reference count equals zero. Otherwise, it is returned
uninitialized. Fix this by always initializing status to zero.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 640ee17199e4 ("platform/surface: aggregator: Allow enabling of events without notifiers")
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20210604210907.25738-2-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>