Documentation/acpi/gpio.md: Fix markdown heading levels

Only the document title should be a top-level heading ('#'). Everything
else should be a second- over lower-level heading ('##').

Also remove the '#' sign at the end of heading lines. "# Foo #" is
mentioned as a valid syntax variant at [1], but it's quite uncommon.

[1]: https://daringfireball.net/projects/markdown/syntax#header

Change-Id: Ida16c3ecaa22e8439007673cb943d04952e19471
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/25678
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

Documentation/acpi/gpio.md

@@ -1,13 +1,13 @@
-# GPIO toggling in ACPI AML for coreboot #
+# GPIO toggling in ACPI AML for coreboot
 
-# Table of contents #
+## Table of contents
 - Introduction
 - Platform Interface
 - Helper routines
 - Implementation details
 - Arguments and Local Variables Management
 
-# Introduction #
+## Introduction
 
 ACPI provides platform-independent interfaces enabling the operating
 system to perform power management for devices as well as the entire
@@ -25,7 +25,7 @@ depend upon platform to do the required work. This document presents a
 simple interface that can be used by any coreboot driver to generate
 ACPI AML code for reading or toggling platform GPIOs.
 
-# Platform Interface #
+## Platform Interface
 
 All platforms that use drivers requiring ACPI AML code for GPIO
 interactions need to be implement the following functions:
@@ -56,7 +56,7 @@ adding them as AML code callbacks for the following reasons:
 3. Allows GPIO AML methods to be present under any device scope and
    gives SoC the flexibility to call them without any restrictions.
 
-# Helper routines #
+## Helper routines
 
 In order to relieve drivers of the task of implementing the same code
 for enabling/disabling Tx GPIOs based on the GPIO polarity, helper
@@ -73,7 +73,7 @@ calling the platform specific acpigen_soc_{set,clear}_tx_gpio
 functions internally. Thus, all the ACPI AML calling conventions for
 the platform functions apply to these helper functions as well.
 
-# Implementation Details #
+## Implementation Details
 
 ACPI library in coreboot will provide weak definitions for all the
 above functions with error messages indicating that these functions
@@ -163,7 +163,7 @@ get/set/clear any GPIO. In order to decide whether GPIO operations are
 required, driver code can rely either on some config option or read
 device-tree to use any user-provided GPIOs.
 
-# Arguments and Local Variables Management #
+## Arguments and Local Variables Management
 
 Platform-defined functions can call methods using the same calling
 conventions provided by AML code. However, use of Local Variables is