drm/i915: Don't leak the DPT if drm_framebuffer_init() fails

We are failing to free the already allocated DPT if the final
drm_framebuffer_init() fails. That would require idr_alloc() to
fail, so not very likely, but let's add the cleanup code anyway.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230215222426.26085-1-ville.syrjala@linux.intel.com


Reviewed-by: Matt Roper <matthew.d.roper@intel.com>