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_gem.c b/drivers/gpu/drm/drm_gem.c
index 83114b5..fc6ded8 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -272,8 +272,7 @@
 	spin_unlock(&file_priv->table_lock);
 	if (ret == -EAGAIN)
 		goto again;
-
-	if (ret != 0)
+	else if (ret)
 		return ret;
 
 	drm_gem_object_handle_reference(obj);
@@ -456,8 +455,7 @@
 
 		if (ret == -EAGAIN)
 			goto again;
-
-		if (ret != 0)
+		else if (ret)
 			goto err;
 
 		/* Allocate a reference for the name table.  */