linux-next: SLIMbus: doc: Fix a warning "Title underline too short"

This patch fixes a warning during "make xmldocs"

Documentation/driver-api/slimbus.rst:93:
WARNING: Title underline too short.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/driver-api/slimbus.rst b/Documentation/driver-api/slimbus.rst
index 7555ecd..a97449c 100644
--- a/Documentation/driver-api/slimbus.rst
+++ b/Documentation/driver-api/slimbus.rst
@@ -90,7 +90,7 @@
 steps to boot the device so that it's functional after the bus has been reset.
 
 Driver and Controller APIs:
---------------------------
+---------------------------
 .. kernel-doc:: include/linux/slimbus.h
    :internal: