doc: imx93_var_som: Adjust the underline length

Adjust the underline length so that it matches the title length.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
diff --git a/doc/board/variscite/imx93_var_som.rst b/doc/board/variscite/imx93_var_som.rst
index 2225a77..4951afd 100644
--- a/doc/board/variscite/imx93_var_som.rst
+++ b/doc/board/variscite/imx93_var_som.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+
 
 imx93_var_som
-=======================
+=============
 
 U-Boot for the Variscite VAR-SOM-MX93 Symphony evaluation board
 
@@ -38,7 +38,7 @@
    $ cp firmware-imx-8.21/firmware/ddr/synopsys/lpddr4*.bin $(srctree)
 
 Get ahab-container.img
----------------------------------------
+----------------------
 
 .. code-block:: bash