Documentation: Fix pci=config_acs= example

Documentation: Fix pci=config_acs= example

The documentation currently says:

  config_acs=
                  Format:
                  <ACS flags>@<pci_dev>[; ...]
                  Specify one or more PCI devices (in the format
                  specified above) optionally prepended with flags
                  and separated by semicolons. The respective
                  capabilities will be enabled, disabled or
                  unchanged based on what is specified in
                  flags.
           (...)
                  For example,
                    pci=config_acs=10x
                  would configure all devices that support
                  ACS to enable P2P Request Redirect, disable
                  Translation Blocking, and leave Source
                  Validation unchanged from whatever power-up
                  or firmware set it to.

See the complete documentation at:

  https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

However, a flag specification always needs to be suffixed with "@" and
a PCI valid device address, which is missing in this example. Also, to
configure all devices that support ACS, the flag needs to be suffixed
with "@pci:0:0", for the ACS support to be enabled.

Fix the documentation so the example is correct.

Link: https://lore.kernel.org/r/20240915-acs-v1-1-b9ee536ee9bd@daynix.com
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>