kconfig: Clean up header comments and make them consistent

Use this short header style in all Kconfig files:

    # <description>

    # <copyright>
    # <license>

    ...

Also change all <description>s from

    # Kconfig[.extension] - Foo-related options

to just

    # Foo-related options

It's clear enough that it's about Kconfig.

The <description> cleanup was done with this command, along with some
manual cleanup (big letter at the start, etc.)

    git ls-files '*Kconfig*' | \
        xargs sed -i -E '1 s/#\s*Kconfig[\w.-]*\s*-\s*/# /'

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
diff --git a/Kconfig.zephyr b/Kconfig.zephyr
index bd17a0b..4ca994a 100644
--- a/Kconfig.zephyr
+++ b/Kconfig.zephyr
@@ -1,11 +1,8 @@
-# Kconfig - general configuration options
+# General configuration options
 
-#
 # Copyright (c) 2014-2015 Wind River Systems, Inc.
 # Copyright (c) 2016 Intel Corporation
-#
 # SPDX-License-Identifier: Apache-2.0
-#
 
 menu "Modules"