docs/man: modify xl-pci-configuration(5) to add 'name' field to PCI_SPEC_STRING

Since assignable devices can be named, a subsequent patch will support use
of a PCI_SPEC_STRING containing a 'name' parameter instead of a 'bdf'. In
this case the name will be used to look up the 'bdf' in the list of assignable
(or assigned) devices.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Acked-by: Wei Liu <wl@xen.org>

docs/man/xl-pci-configuration.5.pod

@@ -51,7 +51,7 @@ is not specified, or if it is specified with an empty value (whether
 positionally or explicitly).
 
 B<NOTE>: In context of B<xl pci-detach> (see L<xl(1)>), parameters other than
-B<bdf> will be ignored.
+B<bdf> or B<name> will be ignored.
 
 =head1 Positional Parameters
 
@@ -70,7 +70,11 @@ B<*> to indicate all functions of a multi-function device.
 
 =item Default Value
 
-None. This parameter is mandatory as it identifies the device.
+None. This parameter is mandatory in its positional form. As a non-positional
+parameter it is also mandatory unless a B<name> parameter is present, in
+which case B<bdf> must not be present since the B<name> will be used to find
+the B<bdf> in the list of assignable devices. See L<xl(1)> for more information
+on naming assignable devices.
 
 =back
 
@@ -194,4 +198,21 @@ B<NOTE>: This overrides the global B<rdm> option.
 
 =back
 
+=item B<name>=I<STRING>
+
+=over 4
+
+=item Description
+
+This is the name given when the B<BDF> was made assignable. See L<xl(1)> for
+more information on naming assignable devices.
+
+=item Default Value
+
+None. This parameter must not be present if a B<bdf> parameter is present.
+If a B<bdf> parameter is not present then B<name> is mandatory as it is
+required to look up the B<BDF> in the list of assignable devices.
+
+=back
+
 =back