drm/i915: Fix memleak in runtime wakeref tracking

If we untrack wakerefs, the actual count may reach zero.
However the krealloced owners array is still there and
needs to be taken care of. Free the owners unconditionally
to fix the leak.

Fixes: bd780f37 ("drm/i915: Track all held rpm wakerefs")
Reported-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190701104442.9319-1-mika.kuoppala@linux.intel.com