scsi: storvsc: remove unnecessary channel inbound lock

In storvsc driver, inbound messages do not go through inbound lock.  The
only effect of this lock was is to provide a barrier for connect and
remove logic.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>