docs/man: modify xl(1) in preparation for naming of assignable devices

A subsequent patch will introduce code to allow a name to be specified to
'xl pci-assignable-add' such that the assignable device may be referred to
by than name in subsequent operations.

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

docs/man/xl.1.pod.in

@@ -1595,19 +1595,23 @@ List virtual network interfaces for a domain.
 
 =over 4
 
-=item B<pci-assignable-list>
+=item B<pci-assignable-list> [I<-n>]
 
 List all the B<BDF> of assignable PCI devices. See
-L<xl-pci-configuration(5)> for more information.
+L<xl-pci-configuration(5)> for more information. If the -n option is
+specified then any name supplied when the device was made assignable
+will also be displayed.
 
 These are devices in the system which are configured to be
 available for passthrough and are bound to a suitable PCI
 backend driver in domain 0 rather than a real driver.
 
-=item B<pci-assignable-add> I<BDF>
+=item B<pci-assignable-add> [I<-n NAME>] I<BDF>
 
 Make the device at B<BDF> assignable to guests. See
-L<xl-pci-configuration(5)> for more information.
+L<xl-pci-configuration(5)> for more information. If the -n option is
+supplied then the assignable device entry will the named with the
+given B<NAME>.
 
 This will bind the device to the pciback driver and assign it to the
 "quarantine domain".  If it is already bound to a driver, it will
@@ -1622,10 +1626,11 @@ not to do this on a device critical to domain 0's operation, such as
 storage controllers, network interfaces, or GPUs that are currently
 being used.
 
-=item B<pci-assignable-remove> [I<-r>] I<BDF>
+=item B<pci-assignable-remove> [I<-r>] I<BDF>|I<NAME>
 
-Make the device at B<BDF> not assignable to guests. See
-L<xl-pci-configuration(5)> for more information.
+Make a device non-assignable to guests. The device may be identified
+either by its B<BDF> or the B<NAME> supplied when the device was made
+assignable. See L<xl-pci-configuration(5)> for more information.
 
 This will at least unbind the device from pciback, and
 re-assign it from the "quarantine domain" back to domain 0.  If the -r