Staging: hv: storvsc: Get rid of the reference counting in struct storvsc_device

Get rid of the reference counting in struct storvsc_device. We manage the lifecycle with
the following logic: If the device is marked for destruction, we dot allow any
outgoing traffic on the device. Incoming traffic is allowed only to drain pending
outgoing traffic. Note that while the upper level code in Linux deals with outstanding
I/Os, we may have situations on Hyper-V where some book keeping messages are sent out
that the upper level Linux code may not be aware of.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>