Documentation: better locations for sysfs-pci, sysfs-tagging

sysfs-pci and sysfs-tagging were mis-filed: their locations within
Documentation/ implied that they were related to file systems. Actually,
each topic is about a very specific *use* of sysfs, and sysfs *happens*
to be a (virtual) filesystem, so this is not really the right place.

It's jarring to be reading about filesystems in general and then come
across these specific details about PCI, and tagging...and then back to
general filesystems again.

Move sysfs-pci to PCI, and move sysfs-tagging to networking. (Thanks to
Jonathan Corbet for coming up with the final locations.)
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/r/20201009070128.118639-1-jhubbard@nvidia.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/PCI/index.rst

@@ -12,6 +12,7 @@ Linux PCI Bus Subsystem
    pciebus-howto
    pci-iov-howto
    msi-howto
+   sysfs-pci
    acpi-info
    pci-error-recovery
    pcieaer-howto

Documentation/filesystems/index.rst

@@ -34,8 +34,6 @@ algorithms work.
    quota
    seq_file
    sharedsubtree
-   sysfs-pci
-   sysfs-tagging
 
    automount-support
 

Documentation/networking/index.rst

@@ -95,6 +95,7 @@ Contents:
    seg6-sysctl
    strparser
    switchdev
+   sysfs-tagging
    tc-actions-env-rules
    tcp-thin
    team