drm/tegra: put drm_gem_object ref on error in tegra_fb_create

Inside tegra_fb_create(), drm_gem_object_lookup() increments ref count of
the found object. But if the following size check fails then the last
found object's ref count should be put there as the unreferencing loop
can't detect this situation.

Found by Linux Verification Center (linuxtesting.org).

Fixes: de2ba664

 ("gpu: host1x: drm: Add memory manager and fb")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231215093356.12067-1-pchelkin@ispras.ru