Docs/subsystem-apis: Remove '[The ]Linux' prefixes from titles of listed documents

Some documents that listed on subsystem-apis have 'Linux' or 'The Linux'
title prefixes.  It's duplicated information, and makes finding the
document of interest with human eyes not easy.  Remove the prefixes from
the titles.
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: Iwona Winiarska <iwona.winiarska@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20230122184834.181977-1-sj@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/PCI/index.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-=======================
-Linux PCI Bus Subsystem
-=======================
+=================
+PCI Bus Subsystem
+=================
 
 .. toctree::
    :maxdepth: 2

Documentation/cpu-freq/index.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-==============================================================================
-Linux CPUFreq - CPU frequency and voltage scaling code in the Linux(TM) kernel
-==============================================================================
+========================================================================
+CPUFreq - CPU frequency and voltage scaling code in the Linux(TM) kernel
+========================================================================
 
 Author: Dominik Brodowski  <linux@brodo.de>
 

Documentation/crypto/index.rst

-=======================
-Linux Kernel Crypto API
-=======================
+==========
+Crypto API
+==========
 
 :Author: Stephan Mueller
 :Author: Marek Vasut

Documentation/driver-api/index.rst

-========================================
-The Linux driver implementer's API guide
-========================================
+==============================
+Driver implementer's API guide
+==============================
 
 The kernel offers a wide variety of interfaces to support the development
 of device drivers.  This document is an only somewhat organized collection

Documentation/gpu/index.rst

-==================================
-Linux GPU Driver Developer's Guide
-==================================
+============================
+GPU Driver Developer's Guide
+============================
 
 .. toctree::
 

Documentation/hwmon/index.rst

-=========================
-Linux Hardware Monitoring
-=========================
+===================
+Hardware Monitoring
+===================
 
 .. toctree::
    :maxdepth: 1

Documentation/input/index.rst

-=============================
-The Linux Input Documentation
-=============================
+===================
+Input Documentation
+===================
 
 Contents:
 

Documentation/mm/index.rst

-=====================================
-Linux Memory Management Documentation
-=====================================
+===============================
+Memory Management Documentation
+===============================
 
 Memory Management Guide
 =======================

Documentation/peci/index.rst

 .. SPDX-License-Identifier: GPL-2.0-only
 
-====================
-Linux PECI Subsystem
-====================
+==============
+PECI Subsystem
+==============
 
 .. toctree::
 

Documentation/scheduler/index.rst

-===============
-Linux Scheduler
-===============
+=========
+Scheduler
+=========
 
 .. toctree::
     :maxdepth: 1

Documentation/scsi/index.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-====================
-Linux SCSI Subsystem
-====================
+==============
+SCSI Subsystem
+==============
 
 .. toctree::
    :maxdepth: 1

Documentation/sound/index.rst

-===================================
-Linux Sound Subsystem Documentation
-===================================
+=============================
+Sound Subsystem Documentation
+=============================
 
 .. toctree::
    :maxdepth: 2

Documentation/virt/index.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-============================
-Linux Virtualization Support
-============================
+======================
+Virtualization Support
+======================
 
 .. toctree::
    :maxdepth: 2

Documentation/watchdog/index.rst

 .. SPDX-License-Identifier: GPL-2.0
 
-======================
-Linux Watchdog Support
-======================
+================
+Watchdog Support
+================
 
 .. toctree::
     :maxdepth: 1