drm: Fix the number of connector and encoder to cleanup functions

It is left out the code to decrease the number of connector and encoder
to the cleanup functions.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>