storvsc: Fix a bug in the layout of the hv_fc_wwn_packet

The hv_fc_wwn_packet is exchanged over vmbus. Make the definition in
Linux match the Windows definition.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Long Li <longli@microsoft.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>