Drivers: hv: vmbus: On write cleanup the logic to interrupt the host

commit 1f6ee4e7d83586c8b10bd4f2f4346353d04ce884 upstream.

Signal the host when we determine the host is to be signaled.
The currrent code determines the need to signal in the ringbuffer
code and actually issues the signal elsewhere. This can result
in the host viewing this interrupt as spurious since the host may also
poll the channel. Make the necessary adjustments.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: Rolf Neugebauer <rolf.neugebauer@docker.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>