drm: Unify and fix idr error handling

The error handling code w.r.t. idr usage looks inconsistent.

In the case of drm_mode_object_get() and drm_ctxbitmap_next() the error
handling is also incomplete.

Unify the code to follow the same pattern always.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
index 325365f..affa629 100644
--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -85,11 +85,12 @@
 	mutex_lock(&dev->struct_mutex);
 	ret = idr_get_new_above(&dev->ctx_idr, NULL,
 				DRM_RESERVED_CONTEXTS, &new_id);
-	if (ret == -EAGAIN) {
-		mutex_unlock(&dev->struct_mutex);
-		goto again;
-	}
 	mutex_unlock(&dev->struct_mutex);
+	if (ret == -EAGAIN)
+		goto again;
+	else if (ret)
+		return ret;
+
 	return new_id;
 }