Staging: hv: Cleanup irq management

Now that vmbus_driver is a  pci driver,
cleanup the irq allocation mess by using the standard
irq allocation mechanisms.

Note that this patch generates an error when the checkpatch
script is run because of the IRQF_SAMPLE_RANDOM flag used in
request_irq() function. This interrupt may be the only
external event this VM will get and consequently if this
flag (IRQF_SAMPLE_RANDOM) is not  specified, experimentally
we have shown that the entropy in the VM will very very low.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Mike Sterling <mike.sterling@microsoft.com>
Signed-off-by: Abhishek Kane <v-abkane@microsoft.com>
Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>