Drivers: scsi: storvsc: Set cmd_per_lun to reflect value supported by the Host

Set cmd_per_lun to reflect value supported by the Host.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>