drm/i915/display: check if compressed_llb was allocated

drm/i915/display: check if compressed_llb was allocated

If we hit the error path here we unconditionally call
i915_gem_stolen_remove_node, even though we only allocate the
compressed_llb on older platforms. Therefore we should first check that
we actually allocated the node before trying to remove it.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/3709
Fixes: 46b2c40e0af3 ("drm/i915/fbc: Allocate llb before cfb")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210701090326.1056452-1-matthew.auld@intel.com