xend: pass-through: Allow multi-function device specifications to be parsed

xend: pass-through: Allow multi-function device specifications to be parsed

The general format is as follows:

  Now: SEQ:BUS:DEV.FUNC[@VSLOT][,OPT...]
  New: SEQ:BUS:DEV.FUNC0-FUNCN[@VSLOT][,OPT...]
       SEQ:BUS:DEV.FUNC0,FUNCM,FUNCN[@VSLOT][,OPT...]
       SEQ:BUS:DEV.*[@VSLOT][,OPT...]

  In the case of unplug the VSLOT and OPT must be omitted.

  Xm expands this notation notation out and passes
  more conventional parameters to qemu-xen.

  E.g:
       0000:00:01.00-03 becomes:
         0000:00:01.00
         0000:00:01.01
         0000:00:01.02
         0000:00:01.03

       0000:00:01.00,03,05,07 becomes:
         0000:00:01.00
         0000:00:01.03
         0000:00:01.05
         0000:00:01.07

       For a device that has functions 0, 1, 2, 3, 5 and 7,
       0000:00:01.* becomes:
         0000:00:01.00
         0000:00:01.01
         0000:00:01.02
         0000:00:01.03
         0000:00:01.05
         0000:00:01.07

Cc: Dexuan Cui <dexuan.cui@intel.com>
Cc: Masaki Kanno <kanno.masaki@jp.fujitsu.com>
Cc: Akio Takebe <takebe_akio@jp.fujitsu.com>
Signed-off-by: Simon Horman <horms@verge.net.au>