drm/v3d: Fix BO stats accounting for dma-buf-imported buffers.

We always decrement at GEM free, so make sure we increment at GEM
creation for dma-bufs.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190207232613.24981-1-eric@anholt.net


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>