doc: shorten overlong title underlines

Title underlines should match the length of the title. Unfortunately
docutils only catches underlines that are too short.

Add some missing empty lines after titles.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/usage/cmd/askenv.rst b/doc/usage/cmd/askenv.rst
index 347bd59..b85cefa 100644
--- a/doc/usage/cmd/askenv.rst
+++ b/doc/usage/cmd/askenv.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 askenv command
-===============
+==============
 
 Synopsis
 --------
diff --git a/doc/usage/cmd/bootdev.rst b/doc/usage/cmd/bootdev.rst
index 6c68d0b..fb638b5 100644
--- a/doc/usage/cmd/bootdev.rst
+++ b/doc/usage/cmd/bootdev.rst
@@ -76,7 +76,7 @@
 
 
 bootdev select
-~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~
 
 Use this to select a particular bootdev. You can select it by the sequence
 number or name, as shown in `bootdev list`.
@@ -89,7 +89,7 @@
 
 
 bootdev info
-~~~~~~~~~~~~~~~
+~~~~~~~~~~~~
 
 This shows information on the current bootdev, with the format looking like
 this:
diff --git a/doc/usage/cmd/cat.rst b/doc/usage/cmd/cat.rst
index 5ef4731..5aaf497 100644
--- a/doc/usage/cmd/cat.rst
+++ b/doc/usage/cmd/cat.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 cat command
-===============
+===========
 
 Synopsis
 --------
diff --git a/doc/usage/cmd/coninfo.rst b/doc/usage/cmd/coninfo.rst
index f913148..76cb6c3 100644
--- a/doc/usage/cmd/coninfo.rst
+++ b/doc/usage/cmd/coninfo.rst
@@ -21,7 +21,7 @@
 list of device names.
 
 Example
---------
+-------
 
 .. code-block:: console
 
diff --git a/doc/usage/cmd/mmc.rst b/doc/usage/cmd/mmc.rst
index c0924ba..8394f64 100644
--- a/doc/usage/cmd/mmc.rst
+++ b/doc/usage/cmd/mmc.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 mmc command
-============
+===========
 
 Synopsis
 --------
diff --git a/doc/usage/cmd/part.rst b/doc/usage/cmd/part.rst
index 8a594aa..eee5225 100644
--- a/doc/usage/cmd/part.rst
+++ b/doc/usage/cmd/part.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 part command
-===============
+============
 
 Synopis
 -------
diff --git a/doc/usage/cmd/wdt.rst b/doc/usage/cmd/wdt.rst
index 8d80433..8bb8b36 100644
--- a/doc/usage/cmd/wdt.rst
+++ b/doc/usage/cmd/wdt.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 wdt command
-============
+===========
 
 Synopsis
 --------
diff --git a/doc/usage/cmd/xxd.rst b/doc/usage/cmd/xxd.rst
index 0de1223..13bb438 100644
--- a/doc/usage/cmd/xxd.rst
+++ b/doc/usage/cmd/xxd.rst
@@ -1,7 +1,7 @@
 .. SPDX-License-Identifier: GPL-2.0+:
 
 xxd command
-===============
+===========
 
 Synopsis
 --------